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

[ruiu]

Summary

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

[fedor.sergeev]

LGTM, nice trick.

[fedor.sergeev]

Though, if you really want to make it LLD-only (as comments suggest) then you better check for LLD :)

[ruiu]

The --color-diagnostics option is supported by lld only at the moment, but we could add the option to other linkers, so I think as long as a linker accepts it, we want to pass that flag.

llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

if (UNIX AND
     CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
     CMAKE_GENERATOR STREQUAL "Ninja")
   append("-fcolor-diagnostics" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 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()
 
 # Add flags for add_dead_strip().
 # FIXME: With MSVS, consider compiling with /Gy and linking with /OPT:REF?
 # But MinSizeRel seems to add that automatically, so maybe disable these
 # flags instead if LLVM_NO_DEAD_STRIP is set.
 if(NOT CYGWIN AND NOT WIN32)