Ignore unknown -fno-builtin-*.

This matches gcc's behavior.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191434 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Driver/Options.td

@@ -584,6 +584,8 @@ def fno_builtin_strcat : Flag<["-"], "fno-builtin-strcat">, Group<f_Group>;
 def fno_builtin_strcpy : Flag<["-"], "fno-builtin-strcpy">, Group<f_Group>;
 def fno_builtin : Flag<["-"], "fno-builtin">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Disable implicit builtin knowledge of functions">;
+def fno_builtin_ : Joined<["-"], "fno-builtin-">, Group<clang_ignored_f_Group>,
+  HelpText<"Disable implicit builtin knowledge of a specific function">;
 def fno_math_builtin : Flag<["-"], "fno-math-builtin">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Disable implicit builtin knowledge of math functions">;
 def fno_caret_diagnostics : Flag<["-"], "fno-caret-diagnostics">, Group<f_Group>,

test/Driver/clang_f_opts.c

@@ -121,4 +121,5 @@
 // RUN:     -fsee -fno-see                                                    \
 // RUN:     -ftracer -fno-tracer                                              \
 // RUN:     -funroll-all-loops -fno-unroll-all-loops                          \
+// RUN:     -fno-builtin-foobar                                               \
 // RUN:     %s