[PowerPC] Add MultiarchIncludeDirs for powerpc64le

There was already partial support for multi-arch on powerpc64le,
but the MultiarchIncludeDirs setting was missing.  This patch
adds the appropriate definition, and also extends the
linux-header-search.cpp test case to verify an Ubuntu 14.04
powerpc64le tree.

llvm-svn: 211359
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index 7157556..6817898 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -3264,6 +3264,9 @@
   const StringRef PPC64MultiarchIncludeDirs[] = {
     "/usr/include/powerpc64-linux-gnu"
   };
+  const StringRef PPC64LEMultiarchIncludeDirs[] = {
+    "/usr/include/powerpc64le-linux-gnu"
+  };
   ArrayRef<StringRef> MultiarchIncludeDirs;
   if (getTriple().getArch() == llvm::Triple::x86_64) {
     MultiarchIncludeDirs = X86_64MultiarchIncludeDirs;
@@ -3287,6 +3290,8 @@
     MultiarchIncludeDirs = PPCMultiarchIncludeDirs;
   } else if (getTriple().getArch() == llvm::Triple::ppc64) {
     MultiarchIncludeDirs = PPC64MultiarchIncludeDirs;
+  } else if (getTriple().getArch() == llvm::Triple::ppc64le) {
+    MultiarchIncludeDirs = PPC64LEMultiarchIncludeDirs;
   }
   for (StringRef Dir : MultiarchIncludeDirs) {
     if (llvm::sys::fs::exists(SysRoot + Dir)) {