[CMake][libcxxabi] Fix the -target and -gcc-toolchain flag handling

[phosek]

Summary

CMake has the problem with the single dash variant because of the space, so use the double dash with equal sign version. These flag need to be included in compile flags to propagate correctly. We also don't have to pass the target triple when checking for compiler-rt since that flag is already included in compile flags now.

[phosek]

Ping, can someone please take a look?

libcxxabi/trunk/CMakeLists.txt

if (${condition})
     list(APPEND ${list} ${var})
   endif()
 endmacro()
 
 macro(add_target_flags_if condition var)
   if (${condition})
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${var}")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${var}")
+    list(APPEND LIBCXXABI_COMPILE_FLAGS ${var})
     list(APPEND LIBCXXABI_LINK_FLAGS ${var})
   endif()
 endmacro()
 
 set(LIBCXXABI_C_FLAGS "")
 set(LIBCXXABI_CXX_FLAGS "")
 set(LIBCXXABI_COMPILE_FLAGS "")
 set(LIBCXXABI_LINK_FLAGS "")
 
 # Configure target flags
 add_target_flags_if(LIBCXXABI_BUILD_32_BITS "-m32")
 add_target_flags_if(LIBCXXABI_TARGET_TRIPLE
-          "-target ${LIBCXXABI_TARGET_TRIPLE}")
+          "--target=${LIBCXXABI_TARGET_TRIPLE}")
 add_target_flags_if(LIBCXXABI_GCC_TOOLCHAIN
-         "-gcc-toolchain ${LIBCXXABI_GCC_TOOLCHAIN}")
+         "--gcc-toolchain=${LIBCXXABI_GCC_TOOLCHAIN}")
 add_target_flags_if(LIBCXXABI_SYSROOT
           "--sysroot=${LIBCXXABI_SYSROOT}")
 
 if (LIBCXXABI_TARGET_TRIPLE)
   set(TARGET_TRIPLE "${LIBCXXABI_TARGET_TRIPLE}")
 endif()
 
 # Configure compiler. Must happen after setting the target flags.

libcxxabi/trunk/cmake/Modules/HandleCompilerRT.cmake

 function(find_compiler_rt_library name dest)
   if (NOT DEFINED LIBCXXABI_COMPILE_FLAGS)
     message(FATAL_ERROR "LIBCXXABI_COMPILE_FLAGS must be defined when using this function")
   endif()
   set(dest "" PARENT_SCOPE)
-  set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${TARGET_TRIPLE} ${LIBCXXABI_COMPILE_FLAGS}
+  set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${LIBCXXABI_COMPILE_FLAGS}
       "--rtlib=compiler-rt" "--print-libgcc-file-name")
   if (CMAKE_CXX_COMPILER_ID MATCHES Clang AND CMAKE_CXX_COMPILER_TARGET)
     list(APPEND CLANG_COMMAND "--target=${CMAKE_CXX_COMPILER_TARGET}")
   endif()
   execute_process(
       COMMAND ${CLANG_COMMAND}
       RESULT_VARIABLE HAD_ERROR
       OUTPUT_VARIABLE LIBRARY_FILE