[clang] Limit scope of CLANG_VENDOR definition

[smeenai]

Summary

It's only used by Version.cpp, so limit the definition to just that one
file instead of making all of Clang recompile if you change CLANG_VENDOR.

[phosek]

LGTM

clang/CMakeLists.txt

set(CLANG_OPENMP_NVPTX_DEFAULT_ARCH ${CUDA_ARCH_MATCH} CACHE STRING
     "Default architecture for OpenMP offloading to Nvidia GPUs.")
 endif()
 
 set(CLANG_SYSTEMZ_DEFAULT_ARCH "z10" CACHE STRING "SystemZ Default Arch")
 
 set(CLANG_VENDOR ${PACKAGE_VENDOR} CACHE STRING
   "Vendor-specific text for showing with version information.")
 
-if( CLANG_VENDOR )
-  add_definitions( -DCLANG_VENDOR="${CLANG_VENDOR} " )
-endif()
-
 set(CLANG_REPOSITORY_STRING "" CACHE STRING
   "Vendor-specific text for showing the repository the source is taken from.")
 
 if(CLANG_REPOSITORY_STRING)
   add_definitions(-DCLANG_REPOSITORY_STRING="${CLANG_REPOSITORY_STRING}")
 endif()
 
 set(CLANG_VENDOR_UTI "org.llvm.clang" CACHE STRING

clang/lib/Basic/CMakeLists.txt

COMMAND ${CMAKE_COMMAND} "-DNAMES=\"LLVM;CLANG\""
                            "-DHEADER_FILE=${version_inc}"
                            -P "${generate_vcs_version_script}")
 
 # Mark the generated header as being generated.
 set_source_files_properties("${version_inc}"
   PROPERTIES GENERATED TRUE
              HEADER_FILE_ONLY TRUE)
 
+if(CLANG_VENDOR)
+  set_source_files_properties(Version.cpp
+    PROPERTIES COMPILE_DEFINITIONS "CLANG_VENDOR=\"${CLANG_VENDOR} \"")
+endif()
+
 add_clang_library(clangBasic
   Attributes.cpp
   Builtins.cpp
   CharInfo.cpp
   CodeGenOptions.cpp
   Cuda.cpp
   Diagnostic.cpp
   DiagnosticIDs.cpp