Rename -show-skipped-includes to -fshow-skipped-includes and make it a driver option

[hans]

Summary

This is a user-facing option, so it doesn't make sense for it to be cc1 only.

Follow-up to D100420

clang/include/clang/Driver/Options.td

def F : JoinedOrSeparate<["-"], "F">, Flags<[RenderJoined,CC1Option]>,
     HelpText<"Add directory to framework include search path">;
 def G : JoinedOrSeparate<["-"], "G">, Flags<[NoXarchOption]>, Group<m_Group>,
     MetaVarName<"<size>">, HelpText<"Put objects of at most <size> bytes "
     "into small data section (MIPS / Hexagon)">;
 def G_EQ : Joined<["-"], "G=">, Flags<[NoXarchOption]>, Group<m_Group>, Alias<G>;
 def H : Flag<["-"], "H">, Flags<[CC1Option]>, Group<Preprocessor_Group>,
     HelpText<"Show header includes and nesting depth">,
     MarshallingInfoFlag<DependencyOutputOpts<"ShowHeaderIncludes">>;
+def fshow_skipped_includes : Flag<["-"], "fshow-skipped-includes">,
+  Flags<[CC1Option]>, HelpText<"Show skipped includes in -H output.">,
+  DocBrief<[{#include files may be "skipped" due to include guard optimization
+             or #pragma once. This flag makes -H show also such includes.}]>,
+  MarshallingInfoFlag<DependencyOutputOpts<"ShowSkippedHeaderIncludes">>;
+
 def I_ : Flag<["-"], "I-">, Group<I_Group>,
     HelpText<"Restrict all prior -I flags to double-quoted inclusion and "
              "remove current directory from include path">;
 def I : JoinedOrSeparate<["-"], "I">, Group<I_Group>,
     Flags<[CC1Option,CC1AsOption,FlangOption,FC1Option]>, MetaVarName<"<dir>">,
     HelpText<"Add directory to the end of the list of include search paths">,
     DocBrief<[{Add directory to include search path. For C++ inputs, if
 there are multiple -I options, these directories are searched

 
 //===----------------------------------------------------------------------===//
 // Dependency Output Options
 //===----------------------------------------------------------------------===//
 
 def sys_header_deps : Flag<["-"], "sys-header-deps">,
   HelpText<"Include system headers in dependency output">,
   MarshallingInfoFlag<DependencyOutputOpts<"IncludeSystemHeaders">>;
-def show_skipped_includes : Flag<["-"], "show-skipped-includes">,
-  HelpText<"Show skipped includes in -H output.">,
-  DocBrief<[{#include files may be "skipped" due to include guard optimization
-             or #pragma once. This flag makes -H show also such includes.}]>,
-  MarshallingInfoFlag<DependencyOutputOpts<"ShowSkippedHeaderIncludes">>;
 def module_file_deps : Flag<["-"], "module-file-deps">,
   HelpText<"Include module files in dependency output">,
   MarshallingInfoFlag<DependencyOutputOpts<"IncludeModuleFiles">>;
 def header_include_file : Separate<["-"], "header-include-file">,
   HelpText<"Filename (or -) to write header include output to">,
   MarshallingInfoString<DependencyOutputOpts<"HeaderIncludeOutputFile">>;
 def show_includes : Flag<["--"], "show-includes">,
   HelpText<"Print cl.exe style /showIncludes to stdout">;

clang/lib/Driver/ToolChains/Clang.cpp

#endif
   }
 
   Args.AddAllArgs(CmdArgs, options::OPT_v);
 
   if (Args.getLastArg(options::OPT_H)) {
     CmdArgs.push_back("-H");
     CmdArgs.push_back("-sys-header-deps");
   }
+  Args.AddAllArgs(CmdArgs, options::OPT_fshow_skipped_includes);
 
   if (D.CCPrintHeaders && !D.CCGenDiagnostics) {
     CmdArgs.push_back("-header-include-file");
     CmdArgs.push_back(!D.CCPrintHeadersFilename.empty()
                           ? D.CCPrintHeadersFilename.c_str()
                           : "-");
     CmdArgs.push_back("-sys-header-deps");
   }