Index: clang/lib/Driver/ToolChains/Linux.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Linux.cpp
+++ clang/lib/Driver/ToolChains/Linux.cpp
@@ -244,9 +244,9 @@
     // With devtoolset on RHEL, we want to add a bin directory that is relative
     // to the detected gcc install, because if we are using devtoolset gcc then
     // we want to use other tools from devtoolset (e.g. ld) instead of the
-    // standard system tools.
-    PPaths.push_back(Twine(GCCInstallation.getParentLibPath() +
-                     "/../bin").str());
+    // standard system tools. This should take precedence over InstalledDir.
+    PPaths.insert(PPaths.begin(),
+                  Twine(GCCInstallation.getParentLibPath() + "/../bin").str());
 
   if (Arch == llvm::Triple::arm || Arch == llvm::Triple::thumb)
     ExtraOpts.push_back("-X");