Add support for generating Swift SDKs for Ubuntu 24.04 Noble (#188)

I was working on adding Debian 12 support for #116, but realized that adding Ubuntu Noble is "low-hanging fruit", since it's very straightforward. The default is still Ubuntu 22.04 Jammy, but this adds the option of generating the Swift SDK for 24.04 Noble now.

```
swift run swift-sdk-generator make-linux-sdk --linux-distribution-version 24.04
```

I have also changed the packages download to get `Packages.xz` instead of `Packages.gz` since it is a smaller file download. I wonder if it is okay to use `xz` here since I noticed that the directories on the Debian mirrors only have `Packages.xz` files available, unlike the Ubuntu mirrors which all have `Packages.gz` AND `Packages.xz` files available.

Brewfile

@@ -0,0 +1 @@
+brew 'xz'

README.md

@@ -27,6 +27,16 @@ swift experimental-sdk list
 The output will either state that no Swift SDKs are available, or produce a list of those you previously had 
 installed, in case you've used the `swift experimental-sdk install` command before.
 
+### macOS Requirements
+
+The generator depends on the `xz` utility for more efficient downloading of package lists for Ubuntu. This is optional, but can be installed via the included `Brewfile`:
+
+```bash
+brew bundle install
+```
+
+If `xz` is not found, the generator will fallback on `gzip`.
+
 ## Supported platforms and minimum versions
 
 macOS as a host platform and Linux as both host and target platforms are supported by the generator.
@@ -36,7 +46,7 @@ The generator also allows cross-compiling between any Linux distributions offici
 | -:             | :-                        | :-                          |
 | macOS (arm64)  | ✅ macOS 13.0+            | ❌                         |
 | macOS (x86_64) | ✅ macOS 13.0+[^1]        | ❌                         |
-| Ubuntu         | ✅ 20.04+                 | ✅ 20.04 / 22.04           |
+| Ubuntu         | ✅ 20.04+                 | ✅ 20.04+                  |
 | RHEL           | ✅ Fedora 39[^2], UBI 9   | ✅ UBI 9                   |
 | Amazon Linux 2 | ✅ Supported              | ✅ Supported[^3]           |
 | Debian 12      | ✅ Supported[^2]          | ✅ Supported[^2][^3]       |

Sources/GeneratorCLI/GeneratorCLI.swift

@@ -199,9 +199,9 @@ extension GeneratorCLI {
 
     @Option(
       help: """
-      Version of the Linux distribution used as a target platform. Available options for Ubuntu: `20.04`, \
-      `22.04` (default when `--linux-distribution-name` is `ubuntu`). Available options for RHEL: `ubi9` (default when \
-      `--linux-distribution-name` is `rhel`).
+      Version of the Linux distribution used as a target platform.
+      Available options for Ubuntu: `20.04`, `22.04` (default when `--linux-distribution-name` is `ubuntu`), `24.04`.
+      Available options for RHEL: `ubi9` (default when `--linux-distribution-name` is `rhel`).
       """
     )
     var linuxDistributionVersion: String?

Sources/SwiftSDKGenerator/Generator/SwiftSDKGenerator+Download.swift

@@ -82,27 +82,39 @@ extension SwiftSDKGenerator {
   ) async throws {
     logger.debug("Parsing Ubuntu packages list...")
 
+    // Find xz path
+    let xzPath = try await which("xz")
+    if xzPath == nil {
+      logger.warning("""
+      The `xz` utility was not found in `PATH`. \
+      Consider installing it for more efficient downloading of package lists.
+      """)
+    }
+
     async let mainPackages = try await client.parseUbuntuPackagesList(
       ubuntuRelease: versionsConfiguration.linuxDistribution.release,
       repository: "main",
       targetTriple: self.targetTriple,
-      isVerbose: self.isVerbose
+      isVerbose: self.isVerbose,
+      xzPath: xzPath
     )
 
     async let updatesPackages = try await client.parseUbuntuPackagesList(
       ubuntuRelease: versionsConfiguration.linuxDistribution.release,
       releaseSuffix: "-updates",
       repository: "main",
       targetTriple: self.targetTriple,
-      isVerbose: self.isVerbose
+      isVerbose: self.isVerbose,
+      xzPath: xzPath
     )
 
     async let universePackages = try await client.parseUbuntuPackagesList(
       ubuntuRelease: versionsConfiguration.linuxDistribution.release,
       releaseSuffix: "-updates",
       repository: "universe",
       targetTriple: self.targetTriple,
-      isVerbose: self.isVerbose
+      isVerbose: self.isVerbose,
+      xzPath: xzPath
     )
 
     let allPackages = try await mainPackages
@@ -175,21 +187,31 @@ extension SwiftSDKGenerator {
 extension HTTPClientProtocol {
   private func downloadUbuntuPackagesList(
     from url: String,
+    unzipWith zipPath: String,
     isVerbose: Bool
   ) async throws -> String? {
-    guard let packages = try await get(url: url).body?.unzip(isVerbose: isVerbose) else {
+    guard let packages = try await get(url: url).body?.unzip(zipPath: zipPath, isVerbose: isVerbose) else {
       throw FileOperationError.downloadFailed(url)
     }
 
     return String(buffer: packages)
   }
 
+  func packagesFileName(isXzAvailable: Bool) -> String {
+    if isXzAvailable {
+      return "Packages.xz"
+    }
+    // Use .gz if xz is not available
+    return "Packages.gz"
+  }
+
   func parseUbuntuPackagesList(
     ubuntuRelease: String,
     releaseSuffix: String = "",
     repository: String,
     targetTriple: Triple,
-    isVerbose: Bool
+    isVerbose: Bool,
+    xzPath: String?
   ) async throws -> [String: URL] {
     let mirrorURL: String
     if targetTriple.arch == .x86_64 {
@@ -200,13 +222,13 @@ extension HTTPClientProtocol {
 
     let packagesListURL = """
     \(mirrorURL)/dists/\(ubuntuRelease)\(releaseSuffix)/\(repository)/binary-\(
-      targetTriple.arch!
-        .debianConventionName
-    )/Packages.gz
+      targetTriple.arch!.debianConventionName
+    )/\(packagesFileName(isXzAvailable: xzPath != nil))
     """
 
     guard let packages = try await downloadUbuntuPackagesList(
       from: packagesListURL,
+      unzipWith: xzPath ?? "/usr/bin/gzip", // fallback on gzip if xz not available
       isVerbose: isVerbose
     ) else {
       throw GeneratorError.ubuntuPackagesDecompressionFailure

Sources/SwiftSDKGenerator/PlatformModels/LinuxDistribution.swift

@@ -10,10 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-private let ubuntuReleases = [
-  "22.04": "jammy",
-]
-
 public enum LinuxDistribution: Hashable, Sendable {
   public enum Name: String {
     case rhel
@@ -27,13 +23,16 @@ public enum LinuxDistribution: Hashable, Sendable {
   public enum Ubuntu: String, Sendable {
     case focal
     case jammy
+    case noble
 
     init(version: String) throws {
       switch version {
       case "20.04":
         self = .focal
       case "22.04":
         self = .jammy
+      case "24.04":
+        self = .noble
       default:
         throw GeneratorError.unknownLinuxDistribution(name: LinuxDistribution.Name.ubuntu.rawValue, version: version)
       }
@@ -43,6 +42,7 @@ public enum LinuxDistribution: Hashable, Sendable {
       switch self {
       case .focal: return "20.04"
       case .jammy: return "22.04"
+      case .noble: return "24.04"
       }
     }
 
@@ -60,7 +60,6 @@ public enum LinuxDistribution: Hashable, Sendable {
           "linux-libc-dev",
           "zlib1g",
           "zlib1g-dev",
-          "libc6",
         ]
       case .jammy: return [
           "libc6",
@@ -75,6 +74,19 @@ public enum LinuxDistribution: Hashable, Sendable {
           "zlib1g",
           "zlib1g-dev",
         ]
+      case .noble: return [
+          "libc6",
+          "libc6-dev",
+          "libgcc-s1",
+          "libgcc-13-dev",
+          "libicu74",
+          "libicu-dev",
+          "libstdc++-13-dev",
+          "libstdc++6",
+          "linux-libc-dev",
+          "zlib1g",
+          "zlib1g-dev",
+        ]
       }
     }
   }

Sources/SwiftSDKGenerator/SystemUtils/ByteBuffer+Utils.swift

@@ -15,9 +15,9 @@ import Foundation
 import NIOCore
 
 public extension ByteBuffer {
-  func unzip(isVerbose: Bool) async throws -> ByteBuffer? {
+  func unzip(zipPath: String, isVerbose: Bool) async throws -> ByteBuffer? {
     let result = try await ProcessExecutor.runCollectingOutput(
-      executable: "/usr/bin/gzip", ["-cd"],
+      executable: zipPath, ["-cd"],
       standardInput: [self].async,
       collectStandardOutput: true,
       collectStandardError: false,

Sources/SwiftSDKGenerator/SystemUtils/which.swift

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2022-2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import AsyncProcess
+import Foundation
+
+/// Look for an executable using the `which` utility.
+/// 
+/// - Parameter executableName: The name of the executable to search for.
+/// - Throws: Any errors thrown by the ProcessExecutor.
+/// - Returns: The path to the executable if found, otherwise nil.
+func which(_ executableName: String) async throws -> String? {
+  let result = try await ProcessExecutor.runCollectingOutput(
+    executable: "/usr/bin/which", [executableName], collectStandardOutput: true, collectStandardError: false,
+    environment: ProcessInfo.processInfo.environment
+  )
+
+  guard result.exitReason == .exit(0) else {
+    return nil
+  }
+
+  if let output = result.standardOutput {
+    let path = String(buffer: output).trimmingCharacters(in: .whitespacesAndNewlines)
+    return path.isEmpty ? nil : path
+  }
+
+  return nil
+}