meson: always use vcs_tag

meson: always use vcs_tag

The branch with configure_file() was broken: meson doesn't know that
this file is a prerequisite for other targets, so partial rebuilds were broken.
Easy reproducer:
  git mv .git{,.no}
  touch meson build && ninja -C build src/basic/libbasic.a
  rm build/version.h
  ninja -C build src/basic/libbasic.a

Using vcs_tag() also in that case makes meson always build the file.

(Combined with the issue fixed in previous commit, I was encountering
failed builds quite often.)

Fixes 3f6ce3d4f04de0f765bb3bde0e400d0823829486.