[Driver] Support g++ headers in include/g++

ray's gcc installation puts C++ headers in PREFIX/include/g++ without
indicating a gcc version at all. Typically this is because the version
is encoded somewhere in PREFIX.

Differential Revision: https://reviews.llvm.org/D53770

llvm-svn: 346802
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 2ac335c..59034bc 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -930,6 +930,9 @@
       // Freescale SDK C++ headers are directly in <sysroot>/usr/include/c++,
       // without a subdirectory corresponding to the gcc version.
       LibDir.str() + "/../include/c++",
+      // Cray's gcc installation puts headers under "g++" without a
+      // version suffix.
+      LibDir.str() + "/../include/g++",
   };
 
   for (const auto &IncludePath : LibStdCXXIncludePathCandidates) {