Add ZeekBundle for integrating third-party components into our builds

This provides an experimental alternative configuration & build approach for
third-party submodules. It introduces a small CMake abstraction that will build
the library separately at configuration time to isolate it from other
targets. Then, we use `find_package` to pick up the (static) library from our
build directory.

For an example of its use, see Broker's CMakeLists.txt.

Co-authored-by: Christian Kreibich <[email protected]>

ZeekBundle.cmake

@@ -0,0 +1,140 @@
+# CMake dependencies.
+include(FetchContent)
+
+# Users may override this path to place the compiled packages elsewhere.
+set(ZEEK_BUNDLE_PREFIX "${PROJECT_BINARY_DIR}/zeek-bundle" CACHE STRING
+    "Path to the Zeek packages cache directory")
+
+# Opt-in to changed CMake behavior for fetch ZIP files.
+if (POLICY CMP0135)
+  cmake_policy(SET CMP0135 NEW)
+endif ()
+
+# Tries to find a package in the Zeek package cache.
+function(ZeekBundle_Find name)
+  find_package(${name} CONFIG QUIET NO_DEFAULT_PATH HINTS ${ZEEK_BUNDLE_PREFIX})
+  if (${name}_FOUND)
+    set(ZeekBundle_FOUND ON PARENT_SCOPE)
+  else()
+    set(ZeekBundle_FOUND OFF PARENT_SCOPE)
+  endif ()
+endfunction()
+
+# Runs the build and install steps for an external project.
+function(ZeekBundle_BuildStep name type binDir)
+  # Build the external project.
+  message(STATUS "Building bundled project: ${name} as ${type}")
+  execute_process(
+    COMMAND
+      "${CMAKE_COMMAND}"
+      --build "${binDir}"
+      --config ${type}
+    OUTPUT_FILE "${binDir}/build${type}.out"
+    ERROR_FILE "${binDir}/build${type}.err"
+    RESULT_VARIABLE buildResult)
+  if (NOT buildResult EQUAL 0)
+    file(READ "${binDir}/build${type}.err" cmakeErr)
+    message(FATAL_ERROR "Failed to build ${name}:\n\n${cmakeErr}")
+  endif ()
+  # Install the external project.
+  message(STATUS "Installing bundled project: ${name} as ${type}")
+  execute_process(
+    COMMAND
+      "${CMAKE_COMMAND}"
+      --build "${binDir}"
+      --config ${type}
+      --target install
+    OUTPUT_FILE "${binDir}/install${type}.out"
+    ERROR_FILE "${binDir}/install${type}.err"
+    RESULT_VARIABLE installResult)
+  if (NOT installResult EQUAL 0)
+    file(READ "${binDir}/install${type}.err" cmakeErr)
+    message(FATAL_ERROR "Failed to install ${name}:\n\n${cmakeErr}")
+  endif ()
+endfunction()
+
+# Builds an external project at configure time.
+function(ZeekBundle_Build name srcDir binDir)
+  # Extra arguments are passed as CMake options to the external project.
+  set(cmakeArgs "")
+  foreach (arg IN LISTS ARGN)
+    list(APPEND cmakeArgs "-D${arg}")
+  endforeach ()
+  # Make sure we can build debug and release versions of the project separately.
+  list(APPEND cmakeArgs "-DCMAKE_DEBUG_POSTFIX=d")
+  # Run CMake for the external project.
+  message(STATUS "Configuring bundled project: ${name}")
+  execute_process(
+    COMMAND
+      "${CMAKE_COMMAND}"
+      -G "${CMAKE_GENERATOR}"
+      ${cmakeArgs}
+      -DBUILD_SHARED_LIBS=OFF
+      -DCMAKE_POSITION_INDEPENDENT_CODE=ON
+      -DENABLE_TESTING=OFF
+      "-DCMAKE_INSTALL_PREFIX=${ZEEK_BUNDLE_PREFIX}"
+      "${srcDir}"
+    WORKING_DIRECTORY "${binDir}"
+    OUTPUT_FILE "${binDir}/cmake.out"
+    ERROR_FILE "${binDir}/cmake.err"
+    RESULT_VARIABLE cmakeResult)
+  if (NOT cmakeResult EQUAL 0)
+    file(READ "${binDir}/cmake.err" cmakeErr)
+    message(FATAL_ERROR "Failed to configure external project ${name}:\n\n${cmakeErr}")
+  endif ()
+  get_property(isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
+  if (isMultiConfig)
+    ZeekBundle_BuildStep(${name} Debug ${binDir})
+    ZeekBundle_BuildStep(${name} Release ${binDir})
+  else ()
+    # On Windows, we cannot mix debug and release libraries.
+    if (WIN32)
+      ZeekBundle_BuildStep(${name} ${CMAKE_BUILD_TYPE} ${binDir})
+    else()
+      ZeekBundle_BuildStep(${name} Release ${binDir})
+    endif()
+  endif ()
+
+
+endfunction ()
+
+# Adds a bundled package to Zeek.
+#
+# Usage:
+# ZeekBundle_Add(
+#   NAME <name>
+#   FETCH (URL <url> | GIT_REPOSITORY <repo> GIT_TAG <tag> | SOURCE_DIR <path>)
+#   [CONFIGURE <args>]
+# )
+function (ZeekBundle_Add)
+  # Parse the function arguments.
+  cmake_parse_arguments(arg "" "NAME" "FETCH;CONFIGURE" ${ARGN})
+  if (NOT arg_NAME)
+    message(FATAL_ERROR "ZeekBundle_Add: mandatory argument NAME is missing!")
+  endif ()
+  if (NOT arg_FETCH)
+    message(FATAL_ERROR "ZeekBundle_Add: mandatory argument FETCH is missing!")
+  endif ()
+  # Use find_package if the user explicitly requested the package.
+  if (DEFINED ${arg_NAME}_ROOT)
+    message(STATUS "ZeekBundle: use system library for ${arg_NAME}")
+    find_package(${arg_NAME} CONFIG QUIET REQUIRED NO_DEFAULT_PATH PATHS ${${arg_NAME}_ROOT})
+    return ()
+  endif ()
+  # Check if we already have the package.
+  ZeekBundle_Find(${arg_NAME})
+  if (ZeekBundle_FOUND)
+    return ()
+  endif ()
+  # Fetch the package by delegating to FetchContent.
+  FetchContent_Declare(dl_${arg_NAME} ${arg_FETCH})
+  string(TOLOWER "dl_${arg_NAME}" internalName)
+  FetchContent_Populate(${internalName})
+  # Build the package and verify that it was found.
+  ZeekBundle_Build(
+    ${arg_NAME}
+    "${${internalName}_SOURCE_DIR}"
+    "${${internalName}_BINARY_DIR}"
+    ${arg_CONFIGURE})
+  find_package(${arg_NAME} CONFIG QUIET REQUIRED NO_DEFAULT_PATH PATHS ${ZEEK_BUNDLE_PREFIX})
+endfunction ()