[driver] Fix so that clang can find correct path prefix for libc object files
from GNU binutils supporting multi-arch folder for ARM target.
Patch by Jiangning Liu <jiangning.liu@arm.com>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160060 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 93df747..b858c3e 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -1905,6 +1905,11 @@
     // common linux triples that don't quite match the Clang triple for both
     // 32-bit and 64-bit targets. Multiarch fixes its install triples to these
     // regardless of what the actual target triple is.
+  case llvm::Triple::arm:
+  case llvm::Triple::thumb:
+    if (llvm::sys::fs::exists(SysRoot + "/lib/arm-linux-gnueabi"))
+      return "arm-linux-gnueabi";
+    return TargetTriple.str();
   case llvm::Triple::x86:
     if (llvm::sys::fs::exists(SysRoot + "/lib/i386-linux-gnu"))
       return "i386-linux-gnu";