archivers/gcab: update to 1.6

Changelog:
New Features:

• Allow specifying the allowed compression formats at runtime (!15) This would allow us, for example, to disable the slightly scary LZX compression format when parsing unknown files. Bugfixes:
• Do not require git when building from a tarball

https://gitlab.gnome.org/GNOME/gcab/-/blob/v1.6/NEWS

While here pet portclippy.

PR: 279024
Approved by: gnome (maintainer, timeout 2 weeks)