Belatedly add the clang patch corresponding to r277423.

contrib/llvm/patches/patch-29-clang-add-mips-triples.diff

@@ -0,0 +1,33 @@
+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
+@@ -6592,6 +6592,17 @@ 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());