Allow clang to be built for mips/mips64 backend types by adding our mips
triple ids

This only allows testing and does not change the defaults for mips/mips64.
They still build/use gcc by default.

Differential Revision:	https://reviews.freebsd.org/D1190
Reviewed by:	dim

Introduced here: http://svnweb.freebsd.org/changeset/base/277423

Index: tools/clang/lib/Driver/Tools.cpp
===================================================================
--- tools/clang/lib/Driver/Tools.cpp
+++ tools/clang/lib/Driver/Tools.cpp
@@ -6652,6 +6652,17 @@ void freebsd::Link::ConstructJob(Compilation &C, c
     CmdArgs.push_back("elf32ppc_fbsd");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_G)) {
+    if (ToolChain.getArch() == llvm::Triple::mips ||
+      ToolChain.getArch() == llvm::Triple::mipsel ||
+      ToolChain.getArch() == llvm::Triple::mips64 ||
+      ToolChain.getArch() == llvm::Triple::mips64el) {
+      StringRef v = A->getValue();
+      CmdArgs.push_back(Args.MakeArgString("-G" + v));
+      A->claim();
+    }
+  }
+
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());