Keeping OptionalObsoleteFiles.inc up to date

Hi,

I'm trying to use "make delete-old" specifying WITHOUT_ keyword for
removing some no-more used set of files.

I've start by testing WITHOUT_TOOLCHAIN:
- Some of files related to clang are correctly delete
- But there are still lot's of others (like /usr/bin/cc)

Then I've checked tools/build/mk/OptionalObsoleteFiles.in and found that
lot's files are missing in the ".if ${MK_TOOLCHAIN} == no" section.

I've started a new run of phk's build_options_survey script:
https://people.freebsd.org/~olivier/build_option_survey_20160406/

And wonder if it's possible to automatically generate the list of
conditional files to be put in OptionalObsoleteFiles.in from the result of
a build_option_survey script ?

Regards,

Olivier