tools: git-version.sh, do not fail when git is not present
tools: git-version.sh, do not fail when git is not present

Signed-off-by: Jiri Slaby <3a42a5d4389f053b0ed9c8486a7a83f2a41a9eea@fi.muni.cz>

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg