.gitignore: consolidate build directory globs
.gitignore: consolidate build directory globs

Summary:
Consolidate the globs used to ignore build directories to remove
unnecessary redundancy.  The new catch-all glob also matches directories
without a version suffix.

Test Plan: Check that everything is still ignored as usual.

Reviewers: hendrikk, tobias, pmaanen

Reviewed By: hendrikk, tobias

Differential Revision: https://dev.openmha.org/D331

HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA,HoerTech-gGmbH/openMHA