Build libm-cdylib only with nightly toolchains

Author: gnzlbg

Cargo.toml

@@ -26,8 +26,8 @@ checked = []
 [workspace]
 members = [
   "crates/compiler-builtins-smoke-test",
-  "crates/libm-cdylib",
   "crates/libm-bench",
+  "crates/libm-cdylib",
 ]
 
 [dev-dependencies]

ci/run.sh

@@ -24,7 +24,7 @@ fi
 $CMD --features "stable checked"
 $CMD --release --features  "stable checked ${TEST_MUSL}"
 
-if rustc --version | grep -E "nightly" ; then
+if rustc --version | grep "nightly" ; then
     if [ "$TARGET" = "x86_64-unknown-linux-gnu" ] || [ "${TARGET}" = "x86_64-apple-darwin" ]; then
         (
             cd crates/libm-cdylib

crates/libm-cdylib/build.rs

@@ -5,4 +5,13 @@ fn main() {
     if profile == "release" {
         println!("cargo:rustc-cfg=release_profile");
     }
+    let nightly = {
+        let mut cmd = std::process::Command::new("rustc");
+        cmd.arg("--version");
+        let output = String::from_utf8(cmd.output().unwrap().stdout).unwrap();
+        output.contains("nightly")
+    };
+    if nightly {
+        println!("cargo:rustc-cfg=unstable_rust");
+    }
 }

crates/libm-cdylib/src/lib.rs

@@ -1,3 +1,10 @@
+#![cfg(
+    // The tests are only enabled on x86 32/64-bit linux/macos:
+    all(unstable_rust,
+        any(target_os = "linux", target_os = "macos"),
+        any(target_arch = "x86", target_arch = "x86_64")
+    )
+)]
 #![allow(dead_code)]
 #![cfg_attr(not(test), feature(core_intrinsics, lang_items))]
 #![cfg_attr(not(test), no_std)]