build: add fallback version for Debian package when not on a tag

Use v0.0.0-snapshot-<short-sha> when no git tag points at HEAD so
dpkg-deb does not fail with empty Version in DEBIAN/control (e.g. on
push to main in CI).

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Acconut

scripts/build_funcs.sh

@@ -3,6 +3,7 @@
 set -e
 
 version="$(git tag -l --points-at HEAD)"
+[[ -z "$version" ]] && version="v0.0.0-snapshot-$(git rev-parse --short HEAD)"
 commit=$(git log --format="%H" -n 1)
 
 function compile {