Use git describe --tag instead of --always

I mistakenly assumed that `git describe --always` would work the same way as
`--tag` in the presence of tags, but it doesn't - it returned bare commit
number. This commit changes this: now both `--tag` and `--always` are used
for the best possible result.

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>