[llvm] [cmake] Add symbolic links for MSVC libraries (PR #106710)

[Mike Hommey via llvm-commits]

https://github.com/glandium created https://github.com/llvm/llvm-project/pull/106710

When cross-compiling a Windows clang with `-DLLVM_BUILD_INSTRUMENTED`, the profiling compiler-rt is linked to binaries, as one would expect, but the profiling compiler-rt contains objects with `/DEFAULTLIB:LIBCMT` and `/DEFAULTLIB:OLDNAMES` directives, which makes the build expect `LIBCMT.lib` and `OLDNAMES.lib`, but they are nowhere to be found because they are in lowercase. While the WinMsvc.cmake helper recreates symbolic links to work around such case sensitivity issues for the Windows SDK libs, it doesn't do so for the MSVC libs, which we add here.

>From caf4ac420f3d02a80673ee41baae1954f2c97515 Mon Sep 17 00:00:00 2001
From: Mike Hommey <mh at glandium.org>
Date: Fri, 30 Aug 2024 18:57:06 +0900
Subject: [PATCH] [cmake] Add symbolic links for MSVC libraries

When cross-compiling a Windows clang with `-DLLVM_BUILD_INSTRUMENTED`,
the profiling compiler-rt is linked to binaries, as one would expect,
but the profiling compiler-rt contains objects with `/DEFAULTLIB:LIBCMT`
and `/DEFAULTLIB:OLDNAMES` directives, which makes the build expect
`LIBCMT.lib` and `OLDNAMES.lib`, but they are nowhere to be found
because they are in lowercase. While the WinMsvc.cmake helper recreates
symbolic links to work around such case sensitivity issues for the
Windows SDK libs, it doesn't do so for the MSVC libs, which we add here.
---
 llvm/cmake/platforms/WinMsvc.cmake | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/llvm/cmake/platforms/WinMsvc.cmake b/llvm/cmake/platforms/WinMsvc.cmake
index e5d1ba8ec4a7c2..40d47f12c53ab7 100644
--- a/llvm/cmake/platforms/WinMsvc.cmake
+++ b/llvm/cmake/platforms/WinMsvc.cmake
@@ -95,6 +95,7 @@ list(APPEND CMAKE_TRY_COMPILE_PLATFORM_VARIABLES
   LLVM_WINSYSROOT
   MSVC_VER
   WINSDK_VER
+  msvc_lib_symlinks_dir
   winsdk_lib_symlinks_dir
   winsdk_vfs_overlay_path
   )
@@ -156,6 +157,24 @@ function(generate_winsdk_lib_symlinks winsdk_um_lib_dir output_dir)
   endforeach()
 endfunction()
 
+function(generate_msvc_lib_symlinks msvc_lib_dir output_dir)
+  execute_process(COMMAND "${CMAKE_COMMAND}" -E make_directory "${output_dir}")
+  file(GLOB libraries RELATIVE "${msvc_lib_dir}" "${msvc_lib_dir}/*.lib")
+  foreach(library ${libraries})
+    get_filename_component(name_wle "${library}" NAME_WLE)
+    get_filename_component(ext "${library}" LAST_EXT)
+    string(TOLOWER "${ext}" lowercase_ext)
+    string(TOUPPER "${name_wle}" all_uppercase_symlink_name_wle)
+    set(uppercase_symlink_name "${all_uppercase_symlink_name_wle}${lowercase_ext}")
+    if(NOT library STREQUAL uppercase_symlink_name)
+      execute_process(COMMAND "${CMAKE_COMMAND}"
+                              -E create_symlink
+                              "${msvc_lib_dir}/${library}"
+                              "${output_dir}/${uppercase_symlink_name}")
+    endif()
+  endforeach()
+endfunction()
+
 function(get_highest_version the_dir the_ver)
   file(GLOB entries LIST_DIRECTORIES true RELATIVE "${the_dir}" "${the_dir}/[0-9.]*")
   foreach(entry ${entries})
@@ -297,6 +316,12 @@ if(case_sensitive_filesystem)
   endif()
   list(APPEND LINK_FLAGS
        -libpath:"${winsdk_lib_symlinks_dir}")
+  if(NOT msvc_lib_symlinks_dir)
+    set(msvc_lib_symlinks_dir "${CMAKE_BINARY_DIR}/msvc_lib_symlinks")
+    generate_msvc_lib_symlinks("${MSVC_LIB}/${WINSDK_ARCH}" "${msvc_lib_symlinks_dir}")
+  endif()
+  list(APPEND LINK_FLAGS
+       -libpath:"${msvc_lib_symlinks_dir}")
 endif()
 
 string(REPLACE ";" " " LINK_FLAGS "${LINK_FLAGS}")