Driver: Make -fwhole-program-vtables a core option so it can be used from clang-cl.

[pcc]

Summary

Also add some missing driver tests for the regular clang driver.

[rnk]

lgtm

clang/include/clang/Driver/Options.td

def fvisibility_EQ : Joined<["-"], "fvisibility=">, Group<f_Group>,
   HelpText<"Set the default symbol visibility for all global declarations">, Values<"hidden,default">;
 def fvisibility_inlines_hidden : Flag<["-"], "fvisibility-inlines-hidden">, Group<f_Group>,
   HelpText<"Give inline C++ member functions default visibility by default">,
   Flags<[CC1Option]>;
 def fvisibility_ms_compat : Flag<["-"], "fvisibility-ms-compat">, Group<f_Group>,
   HelpText<"Give global types 'default' visibility and global functions and "
            "variables 'hidden' visibility by default">;
 def fwhole_program_vtables : Flag<["-"], "fwhole-program-vtables">, Group<f_Group>,
-  Flags<[CC1Option]>,
+  Flags<[CoreOption, CC1Option]>,
   HelpText<"Enables whole-program vtable optimization. Requires -flto">;
-def fno_whole_program_vtables : Flag<["-"], "fno-whole-program-vtables">, Group<f_Group>;
+def fno_whole_program_vtables : Flag<["-"], "fno-whole-program-vtables">, Group<f_Group>,
+  Flags<[CoreOption]>;
 def fwrapv : Flag<["-"], "fwrapv">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Treat signed integer overflow as two's complement">;
 def fwritable_strings : Flag<["-"], "fwritable-strings">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Store string literals as writable data">;
 def fzero_initialized_in_bss : Flag<["-"], "fzero-initialized-in-bss">, Group<f_Group>;
 def ffunction_sections : Flag<["-"], "ffunction-sections">, Group<f_Group>,
   Flags<[CC1Option]>,
   HelpText<"Place each function in its own section (ELF Only)">;

clang/test/Driver/whole-program-vtables.c

 // RUN: %clang -target x86_64-unknown-linux -fwhole-program-vtables -### %s 2>&1 | FileCheck --check-prefix=NO-LTO %s
+// RUN: %clang_cl --target=x86_64-pc-win32 -fwhole-program-vtables -### %s 2>&1 | FileCheck --check-prefix=NO-LTO %s
 // NO-LTO: invalid argument '-fwhole-program-vtables' only allowed with '-flto'
+
+// RUN: %clang -target x86_64-unknown-linux -fwhole-program-vtables -flto -### %s 2>&1 | FileCheck --check-prefix=LTO %s
+// RUN: %clang_cl --target=x86_64-pc-win32 -fwhole-program-vtables -flto -### %s 2>&1 | FileCheck --check-prefix=LTO %s
+// LTO: "-fwhole-program-vtables"
+
+// RUN: %clang -target x86_64-unknown-linux -fwhole-program-vtables -fno-whole-program-vtables -flto -### %s 2>&1 | FileCheck --check-prefix=LTO-DISABLE %s
+// RUN: %clang_cl --target=x86_64-pc-win32 -fwhole-program-vtables -fno-whole-program-vtables -flto -### %s 2>&1 | FileCheck --check-prefix=LTO-DISABLE %s
+// LTO-DISABLE-NOT: "-fwhole-program-vtables"