Treat -g1 as -gline-tables-only

-g1 on gcc (and also IBM's xlc) are documented to be very similar to
-gline-tables-only. Our -gline-tables-only might still be more verbose than -g1
on other compilers, but currently we treat -g1 as -g, and so we're producing
much more debug info at -g1 than everybody else. Treating -g1 as
-gline-tables-only brings us much closer to what everyone else is doing.

For more information, see the discussion on
http://lists.cs.uiuc.edu/pipermail/cfe-dev/2014-October/039649.html

llvm-svn: 220311
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 151400c..822d55b 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3146,7 +3146,8 @@
   // are preserved, all other debug options are substituted with "-g".
   Args.ClaimAllArgs(options::OPT_g_Group);
   if (Arg *A = Args.getLastArg(options::OPT_g_Group)) {
-    if (A->getOption().matches(options::OPT_gline_tables_only)) {
+    if (A->getOption().matches(options::OPT_gline_tables_only) ||
+        A->getOption().matches(options::OPT_g1)) {
       // FIXME: we should support specifying dwarf version with
       // -gline-tables-only.
       CmdArgs.push_back("-gline-tables-only");