multimedia/wl-screenrec: make --version report Git hash

Based on git describe --tags. As upstream doesn't have any tags yet
use snapshot date as an offset with a synthetic tag to unbreak build.

$ wl-screenrec --version
-wl-screenrec 0.1.0
+wl-screenrec 0.1.0-s20230716-g20c6da9

(cherry picked from commit aa953ce86cbf06c8cbd3577ff633c57674e1f6f4)