Add -ftls-model command-line flag.

This allows for setting the default TLS model. (PR9788)

llvm-svn: 159336
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index c3ea22f..c5a837f 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2209,6 +2209,8 @@
 
   Args.AddLastArg(CmdArgs, options::OPT_fvisibility_inlines_hidden);
 
+  Args.AddLastArg(CmdArgs, options::OPT_ftlsmodel_EQ);
+
   // -fhosted is default.
   if (Args.hasFlag(options::OPT_ffreestanding, options::OPT_fhosted, false) ||
       KernelOrKext)