[cmake] Work around more -Wunused-driver-argument warnings

add_compiler_rt_object_libraries should strip out the -msse3 option on
non-macOS Apple platforms.

llvm-svn: 312688
diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
index 622292e..700c31f 100644
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
@@ -56,8 +56,15 @@
 
   foreach(libname ${libnames})
     add_library(${libname} OBJECT ${LIB_SOURCES})
+
+    # Strip out -msse3 if this isn't macOS.
+    set(target_flags ${LIB_CFLAGS})
+    if(APPLE AND NOT "${libname}" MATCHES ".*\.osx.*")
+      list(REMOVE_ITEM target_flags "-msse3")
+    endif()
+
     set_target_compile_flags(${libname}
-      ${CMAKE_CXX_FLAGS} ${extra_cflags_${libname}} ${LIB_CFLAGS})
+      ${CMAKE_CXX_FLAGS} ${extra_cflags_${libname}} ${target_flags})
     set_property(TARGET ${libname} APPEND PROPERTY
       COMPILE_DEFINITIONS ${LIB_DEFS})
     set_target_properties(${libname} PROPERTIES FOLDER "Compiler-RT Libraries")