Use --color-diagnostics instead of -color-diagnostics.

Solaris ld interprets -color-diagnostics as a -c option, so it is
better to use --color-diagnostics instead. lld accepts both.

Differential Revision: https://reviews.llvm.org/D35327

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307850 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/HandleLLVMOptions.cmake

@@ -686,8 +686,8 @@ endif()
 # lld doesn't print colored diagnostics when invoked from Ninja
 if (UNIX AND CMAKE_GENERATOR STREQUAL "Ninja")
   include(CheckLinkerFlag)
-  check_linker_flag("-Wl,-color-diagnostics" LINKER_SUPPORTS_COLOR_DIAGNOSTICS)
-  append_if(LINKER_SUPPORTS_COLOR_DIAGNOSTICS "-Wl,-color-diagnostics"
+  check_linker_flag("-Wl,--color-diagnostics" LINKER_SUPPORTS_COLOR_DIAGNOSTICS)
+  append_if(LINKER_SUPPORTS_COLOR_DIAGNOSTICS "-Wl,--color-diagnostics"
     CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
 endif()