[driver] Ignore -fno-var-tracking; it's a GCC option we don't support.

-fvar-tracking (which IIUC is on by default in GCC) will still generate
an error.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191439 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Driver/Options.td

@@ -800,6 +800,8 @@ def funwind_tables : Flag<["-"], "funwind-tables">, Group<f_Group>;
 def fuse_cxa_atexit : Flag<["-"], "fuse-cxa-atexit">, Group<f_Group>;
 def fuse_init_array : Flag<["-"], "fuse-init-array">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Use .init_array instead of .ctors">;
+def fno_var_tracking : Flag<["-"], "fno-var-tracking">,
+  Group<clang_ignored_f_Group>;
 def fverbose_asm : Flag<["-"], "fverbose-asm">, Group<f_Group>;
 def fvisibility_EQ : Joined<["-"], "fvisibility=">, Group<f_Group>,
   HelpText<"Set the default symbol visibility for all global declarations">;

test/Driver/clang_f_opts.c

@@ -123,4 +123,5 @@
 // RUN:     -funroll-all-loops -fno-unroll-all-loops                          \
 // RUN:     -fno-builtin-foobar                                               \
 // RUN:     -fno-builtin-strcat -fno-builtin-strcpy                           \
+// RUN:     -fno-var-tracking                                                 \
 // RUN:     %s