commit dca95b70ad4433bc478571e967a4be9e830976ee
Author: Chris Bieneman <beanz@apple.com>
Date:   Mon Feb 8 13:20:04 2016 -0800

    [CMake] Fix for clang order file generation on Linux.
    
    In llvm.org r259862 I broke the Linux link step. This patch should fix it.

diff --git a/tools/driver/CMakeLists.txt b/tools/driver/CMakeLists.txt
index 3645734..dc6cd4d 100644
--- a/tools/driver/CMakeLists.txt
+++ b/tools/driver/CMakeLists.txt
@@ -89,12 +89,24 @@ if (APPLE)
   set(TOOL_INFO_BUILD_VERSION)
 endif()
 
-check_cxx_compiler_flag("-Wl,-order_file,${CLANG_ORDER_FILE}"
-  LINKER_HAS_ORDER_FILE_FLAG)
+if(CLANG_ORDER_FILE)
+  include(CMakePushCheckState)
 
-if(LINKER_HAS_ORDER_FILE_FLAG AND CLANG_ORDER_FILE)
-  target_link_libraries(clang "-Wl,-order_file,${CLANG_ORDER_FILE}")
-  set_target_properties(clang PROPERTIES LINK_DEPENDS ${CLANG_ORDER_FILE})
+  function(check_linker_flag flag out_var)
+    cmake_push_check_state()
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${flag}")
+    check_cxx_compiler_flag("" ${out_var})
+    cmake_pop_check_state()
+  endfunction()
+
+  # This is a test to ensure the actual order file works with the linker.
+  check_linker_flag("-Wl,-order_file,${CLANG_ORDER_FILE}"
+    LINKER_ORDER_FILE_WORKS)
+  
+  if(LINKER_ORDER_FILE_WORKS)
+    target_link_libraries(clang "-Wl,-order_file,${CLANG_ORDER_FILE}")
+    set_target_properties(clang PROPERTIES LINK_DEPENDS ${CLANG_ORDER_FILE})
+  endif()
 endif()
 
 if(WITH_POLLY AND LINK_POLLY_INTO_TOOLS)