[cmake] Fix _GNU_SOURCE being added unconditionally

[Trass3r]

clang/CMakeLists.txt

417

Found when building with clang-cl. It's already handled correctly in the llvm config file.

[tstellar]

I think this looks OK. What kind of errors were you seeing before this fix?

[Trass3r]

I only came across it when testing a PCH build.
https://github.com/Trass3r/llvm-project/actions/runs/3423679621/jobs/5702548183

Warning: <built-in>(1,9): warning: definition of macro '_GNU_SOURCE' does not match definition in precompiled header [-Wclang-cl-pch]

It was set for clang but not for llvm when building with clang-cl.

[Trass3r]

Thanks could you also commit it?

[tstellar]

In D137917#3925161, @Trass3r wrote:

Thanks could you also commit it?

Sure, what name and email should I use for you when committing?

[Trass3r]

This comment was removed by Trass3r.

clang/CMakeLists.txt

install(FILES utils/bash-autocomplete.sh
           COMPONENT bash-autocomplete)
   if(NOT LLVM_ENABLE_IDE)
     add_llvm_install_targets(install-bash-autocomplete
                              DEPENDS bash-autocomplete
                              COMPONENT bash-autocomplete)
   endif()
 endif()
 
-add_definitions( -D_GNU_SOURCE )
-
 option(CLANG_BUILD_TOOLS
   "Build the Clang tools. If OFF, just generate build targets." ON)
 
 if(LLVM_ENABLE_PLUGINS OR LLVM_EXPORT_SYMBOLS_FOR_PLUGINS)
   set(HAVE_CLANG_PLUGIN_SUPPORT ON)
 else()
   set(HAVE_CLANG_PLUGIN_SUPPORT OFF)
 endif()

llvm/cmake/config-ix.cmake

# environments.
   set(HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC 0)
 else()
   CHECK_STRUCT_HAS_MEMBER("struct stat" st_mtim.tv_nsec
       "sys/types.h;sys/stat.h" HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC)
 endif()
 
 check_symbol_exists(__GLIBC__ stdio.h LLVM_USING_GLIBC)
 if( LLVM_USING_GLIBC )
-  add_definitions( -D_GNU_SOURCE )
+  add_compile_definitions(_GNU_SOURCE)
   list(APPEND CMAKE_REQUIRED_DEFINITIONS "-D_GNU_SOURCE")
 endif()
 # This check requires _GNU_SOURCE
 if (NOT PURE_WINDOWS)
   if (LLVM_PTHREAD_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES ${LLVM_PTHREAD_LIB})
   endif()
   check_symbol_exists(pthread_getname_np pthread.h HAVE_PTHREAD_GETNAME_NP)