Revert r312240

The buildbots have shown that -Wstrict-prototypes behaves differently in GCC
and Clang so we should keep it disabled until Clang follows GCC's behaviour


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312246 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/HandleLLVMOptions.cmake

@@ -581,8 +581,6 @@ if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
 
   # Enable -Wstring-conversion to catch misuse of string literals.
   add_flag_if_supported("-Wstring-conversion" STRING_CONVERSION_FLAG)
-  # Enable -Wstrict-prototypes to catch incorrectly declared functions in C.
-  add_flag_if_supported("-Wstrict-prototypes" STRICT_PROTOTYPES_FLAG)
 endif (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
 
 if (LLVM_COMPILER_IS_GCC_COMPATIBLE AND NOT LLVM_ENABLE_WARNINGS)