ci: fix new api dev build meta script

Run the set-api-build-metadata on merge requests for testing

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2351>

scripts/set-api-build-metadata.sh

@@ -10,8 +10,12 @@ error() {
   exit 1
 }
 
+command -v git > /dev/null || error "git command not found!"
 command -v poetry > /dev/null || error "poetry command not found!"
 
+# We assume this script only runs in a git repository
+cd "$(git rev-parse --show-toplevel)/api"
+
 COMMIT_SHA="$1"
 
 CURRENT_VERSION="$(poetry version --short)"