Do not add -gsplit-dwarf to LLVM_DEFINITIONS.

[pcc]

Summary

This would cause the flag to appear in the output of "llvm-config --cppflags",
which should contain only preprocessor flags. The -gsplit-dwarf flag in
particular can cause problems with certain downstream users such as cgo.

[dblaikie]

Works for me

[pcc]

Closed by commit rL220410 (authored by @pcc).

llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

if (LLVM_ON_UNIX)
     endif()
   else()
     message(WARNING "LLVM_USE_SANITIZER is not supported on this platform.")
   endif()
 endif()
 
 # Turn on -gsplit-dwarf if requested
 if(LLVM_USE_SPLIT_DWARF)
-  add_llvm_definitions("-gsplit-dwarf")
+  add_definitions("-gsplit-dwarf")
 endif()
 
 add_llvm_definitions( -D__STDC_CONSTANT_MACROS )
 add_llvm_definitions( -D__STDC_FORMAT_MACROS )
 add_llvm_definitions( -D__STDC_LIMIT_MACROS )
 
 # clang doesn't print colored diagnostics when invoked from Ninja
 if (UNIX AND