Push OpenMP linker flags after linker input on Darwin. Don't add any
libraries if -nostdlib is specified. Test.

llvm-svn: 248424
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 949932d..8e8a232 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -6749,8 +6749,6 @@
 
   Args.AddAllArgs(CmdArgs, options::OPT_L);
 
-  addOpenMPRuntime(CmdArgs, getToolChain(), Args);
-
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs);
   // Build the input file for -filelist (list of linker input files) in case we
   // need it later
@@ -6769,6 +6767,10 @@
     InputFileList.push_back(II.getFilename());
   }
 
+  if (!Args.hasArg(options::OPT_nostdlib) &&
+      !Args.hasArg(options::OPT_nodefaultlibs))
+    addOpenMPRuntime(CmdArgs, getToolChain(), Args);
+
   if (isObjCRuntimeLinked(Args) && !Args.hasArg(options::OPT_nostdlib) &&
       !Args.hasArg(options::OPT_nodefaultlibs)) {
     // We use arclite library for both ARC and subscripting support.