fix a bug introduced in my previous patch: moving clang headers to the
"after" group instead of the system group makes it so #include <limits.h>
picks up the *system* limits.h file before clang's.  This causes a failure
on linux and is definitely not what we want.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@65026 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/clang.cpp b/Driver/clang.cpp
index 79166fb..525c27f 100644
--- a/Driver/clang.cpp
+++ b/Driver/clang.cpp
@@ -1098,8 +1098,11 @@
     MainExecutablePath.eraseComponent();  // Remove /clang from foo/bin/clang
     MainExecutablePath.eraseComponent();  // Remove /bin   from foo/bin
     MainExecutablePath.appendComponent("Headers"); // Get foo/Headers
-    Init.AddPath(MainExecutablePath.c_str(), InitHeaderSearch::After,
-                 false, false, false);
+    
+    // We pass true to ignore sysroot so that we *always* look for clang headers
+    // relative to our executable, never relative to -isysroot.
+    Init.AddPath(MainExecutablePath.c_str(), InitHeaderSearch::System,
+                 false, false, false, true /*ignore sysroot*/);
   }
   
   if (!nostdinc)