Fix build on 12.0-CURRENT

Exclude util/c.py (a symlink to util/util.py) from SHEBANG_FILES.

The build currently fails in the patch phase with:

sed: util/c.py: in-place editing only works for regular files

This seems to be caused by base r313277.

While here also simplify RUN_DEPENDS.

PR: 219982
Reported by: antoine, pkg-fallout
Approved by: mat (mentor)
Differential Revision: https://reviews.freebsd.org/D11242