Optionally exclude implicit link directories via environment

A misconfigured compiler may pass extraneous implicit link directories
to its linker.  If they are in `CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES`,
CMake may generate extra `-L` flags on mixed-language link lines that
break linking.  Add an environment variable that users can set to work
around such misconfiguration of their compilers.

Help/envvar/CMAKE_LANG_IMPLICIT_LINK_DIRECTORIES_EXCLUDE.rst

@@ -0,0 +1,13 @@
+CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES_EXCLUDE
+----------------------------------------------
+
+.. versionadded:: 3.27
+
+.. include:: ENV_VAR.txt
+
+A :ref:`semicolon-separated list <CMake Language Lists>` of directories
+to exclude from the :variable:`CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES`
+variable when it is automatically detected from the ``<LANG>`` compiler.
+
+This may be used to work around misconfigured compiler drivers that pass
+extraneous implicit link directories to their linker.

Help/manual/cmake-env-variables.7.rst

@@ -50,6 +50,7 @@ Environment Variables that Control the Build
    /envvar/CMAKE_GENERATOR_TOOLSET
    /envvar/CMAKE_INSTALL_MODE
    /envvar/CMAKE_LANG_COMPILER_LAUNCHER
+   /envvar/CMAKE_LANG_IMPLICIT_LINK_DIRECTORIES_EXCLUDE
    /envvar/CMAKE_LANG_LINKER_LAUNCHER
    /envvar/CMAKE_MSVCIDE_RUN_PATH
    /envvar/CMAKE_NO_VERBOSE

Help/variable/CMAKE_LANG_IMPLICIT_LINK_DIRECTORIES.rst

@@ -6,9 +6,14 @@ Implicit linker search path detected for language ``<LANG>``.
 Compilers typically pass directories containing language runtime
 libraries and default library search paths when they invoke a linker.
 These paths are implicit linker search directories for the compiler's
-language.  For each language enabled by the :command:`project` or
+language.
+
+For each language enabled by the :command:`project` or
 :command:`enable_language` command, CMake automatically detects these
 directories and reports the results in this variable.
+The :envvar:`CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES_EXCLUDE` environment
+variable may be set to exclude specific directories from the automatically
+detected results.
 
 When linking to a static library, CMake adds the implicit link directories
 from this variable for each language used in the static library (except

Modules/CMakeDetermineCompilerABI.cmake

@@ -181,6 +181,10 @@ function(CMAKE_DETERMINE_COMPILER_ABI lang src)
         endif()
       endif()
 
+      if(DEFINED ENV{CMAKE_${lang}_IMPLICIT_LINK_DIRECTORIES_EXCLUDE})
+        list(REMOVE_ITEM implicit_dirs $ENV{CMAKE_${lang}_IMPLICIT_LINK_DIRECTORIES_EXCLUDE})
+      endif()
+
       set(CMAKE_${lang}_IMPLICIT_LINK_LIBRARIES "${implicit_libs}" PARENT_SCOPE)
       set(CMAKE_${lang}_IMPLICIT_LINK_DIRECTORIES "${implicit_dirs}" PARENT_SCOPE)
       set(CMAKE_${lang}_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES "${implicit_fwks}" PARENT_SCOPE)

Tests/RunCMake/ParseImplicitLinkInfo/ExcludeDirs.cmake

@@ -0,0 +1,10 @@
+include("${info}")
+list(GET INFO_CMAKE_C_IMPLICIT_LINK_DIRECTORIES -1 last_dir)
+set(ENV{CMAKE_C_IMPLICIT_LINK_DIRECTORIES_EXCLUDE} "${last_dir}")
+enable_language(C)
+message(STATUS "INFO_CMAKE_C_IMPLICIT_LINK_DIRECTORIES=[${INFO_CMAKE_C_IMPLICIT_LINK_DIRECTORIES}]")
+message(STATUS "ENV{CMAKE_C_IMPLICIT_LINK_DIRECTORIES_EXCLUDE}=[$ENV{CMAKE_C_IMPLICIT_LINK_DIRECTORIES_EXCLUDE}]")
+message(STATUS "CMAKE_C_IMPLICIT_LINK_DIRECTORIES=[${CMAKE_C_IMPLICIT_LINK_DIRECTORIES}]")
+if("${last_dir}" IN_LIST CMAKE_C_IMPLICIT_LINK_DIRECTORIES)
+  message(FATAL_ERROR "${last_dir} was not excluded!")
+endif()

Tests/RunCMake/ParseImplicitLinkInfo/Inspect.cmake

@@ -0,0 +1,12 @@
+enable_language(C)
+
+set(info "")
+foreach(var
+    CMAKE_C_IMPLICIT_LINK_DIRECTORIES
+    )
+  if(DEFINED ${var})
+    string(APPEND info "set(INFO_${var} \"${${var}}\")\n")
+  endif()
+endforeach()
+
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/info.cmake" "${info}")

Tests/RunCMake/ParseImplicitLinkInfo/RunCMakeTest.cmake

@@ -1,3 +1,11 @@
 include(RunCMake)
 
 run_cmake(ParseImplicitLinkInfo)
+
+run_cmake(Inspect)
+set(info "${RunCMake_BINARY_DIR}/Inspect-build/info.cmake")
+include("${info}")
+
+if(INFO_CMAKE_C_IMPLICIT_LINK_DIRECTORIES MATCHES ";")
+  run_cmake_with_options(ExcludeDirs "-Dinfo=${RunCMake_BINARY_DIR}/Inspect-build/info.cmake")
+endif()