Correctly find builtins library with clang-cl

[thieta]

Summary

When using COMPILER_RT_USE_BUILTINS_LIBRARY=ON and clang-cl there
where several places where it didn't work as expected.

First -print-libgcc-file-name has to be prefixed with /clang:

Then the regex that matched the builtins library was wrong because
the builtins library is called clang_rt.builtins_<arch>.lib
and the regex only matched libclang_rt.builtins_arch.a

With this commit you can use a runtime build on Windows with this
option enabled.

[thieta]

Removed erronous change

[thieta]

Ping, anyone care to review this one?

[phosek]

cmake/Modules/HandleCompilerRT.cmake

61

Leftover debugging output?

[thieta]

Removed debug print

[thieta]

Removed the debug message()

cmake/Modules/HandleCompilerRT.cmake

61

whoops. yeah fixed.

[thieta]

ping @phosek - I removed the debug line. do you have any other comments on this one?

[phosek]

LGTM

cmake/Modules/HandleCompilerRT.cmake

if(NOT DEFINED COMPILER_RT_LIBRARY_builtins_${target})
     # set it with cache_compiler_rt_library.
     set(clang_command ${CMAKE_CXX_COMPILER} "${ARG_FLAGS}")
     if(target)
       list(APPEND clang_command "--target=${target}")
     endif()
     get_property(cxx_flags CACHE CMAKE_CXX_FLAGS PROPERTY VALUE)
     string(REPLACE " " ";" cxx_flags "${cxx_flags}")
     list(APPEND clang_command ${cxx_flags})
+    set(cmd_prefix "")
+    if(MSVC AND ${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
+      set(cmd_prefix "/clang:")
+    endif()
     execute_process(
-      COMMAND ${clang_command} "--rtlib=compiler-rt" "-print-libgcc-file-name"
+      COMMAND ${clang_command} "${cmd_prefix}--rtlib=compiler-rt" "${cmd_prefix}-print-libgcc-file-name"
       RESULT_VARIABLE had_error
       OUTPUT_VARIABLE library_file
     )
     string(STRIP "${library_file}" library_file)
     file(TO_CMAKE_PATH "${library_file}" library_file)
     get_filename_component(dirname ${library_file} DIRECTORY)
     if(APPLE)
       execute_process(
         COMMAND ${clang_command} "--print-resource-dir"
         RESULT_VARIABLE had_error
         OUTPUT_VARIABLE resource_dir
       )
       string(STRIP "${resource_dir}" resource_dir)
       set(dirname "${resource_dir}/lib/darwin")
     endif()
     get_filename_component(basename ${library_file} NAME)
-    if(basename MATCHES "libclang_rt\.([a-z0-9_\-]+)\.a")
+    if(basename MATCHES ".*clang_rt\.([a-z0-9_\-]+)\.(a|lib)")
       set(from_name ${CMAKE_MATCH_1})
       get_component_name(${CMAKE_MATCH_1} to_name)
       string(REPLACE "${from_name}" "${to_name}" basename "${basename}")
       set(library_file "${dirname}/${basename}")
       cache_compiler_rt_library(${had_error} builtins "${target}" "${library_file}")
     endif()
   endif()
   if(NOT COMPILER_RT_LIBRARY_builtins_${target})
     set(${variable} "NOTFOUND" PARENT_SCOPE)
     return()
   endif()
   if(NOT DEFINED COMPILER_RT_LIBRARY_${name}_${target})
     # Clang gives only the builtins library path. Other library paths are
     # obtained by substituting "builtins" with ${name} in the builtins
     # path and then checking if the resultant path exists. The result of
     # this check is also cached by cache_compiler_rt_library.
     set(library_file "${COMPILER_RT_LIBRARY_builtins_${target}}")
-    if(library_file MATCHES ".*libclang_rt\.([a-z0-9_\-]+)\.a")
+    if(library_file MATCHES ".*clang_rt\.([a-z0-9_\-]+)\.(a|lib)")
       set(from_name ${CMAKE_MATCH_0})
       get_component_name(${name} to_name)
       string(REPLACE "${from_name}" "${to_name}" library_file "${library_file}")
       cache_compiler_rt_library(FALSE "${name}" "${target}" "${library_file}")
     endif()
   endif()
   set(${variable} "${COMPILER_RT_LIBRARY_${name}_${target}}" PARENT_SCOPE)
 endfunction()