Reapply r284383. The test failures were due to a missing dir in test/

llvm-svn: 284392
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index 93beab8..b51ae1c 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -2970,7 +2970,7 @@
   if (getVFS().exists(InstallRelDir = InstalledDir + "/../target"))
     return InstallRelDir;
 
-  return InstallRelDir;
+  return InstalledDir;
 }
 
 Optional<unsigned> HexagonToolChain::getSmallDataThreshold(