[Bug preprocessor/99343] New: Suggest: -H option support output to file

[chen3feng at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99343

            Bug ID: 99343
           Summary: Suggest: -H option support output to file
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chen3feng at gmail dot com
  Target Milestone: ---

I use the `-H` option to analyze the header file dependency. but it is mixed
with other diagnostic messages, so I have to use an awk script to split them,
this solution is boring and error-prone.

I suggest adding a `-HF` option (similar to the relationship of -MM and -MF
option), which all output this information to a dedicated file.

I also suggest using `-HH` to output only non-system header files.

I'd like to contribute if this suggestion is accepted.

Thanks.