Update tools/dep_updaters/update-test426-fixtures.sh

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: Trott

tools/dep_updaters/update-test426-fixtures.sh

@@ -9,7 +9,12 @@ README="$BASE_DIR/test/test426/README.md"
 TARBALL_URL=$(curl -fsIo /dev/null -w '%header{Location}' https://github.com/tc39/source-map-tests/archive/HEAD.tar.gz)
 SHA=$(basename "$TARBALL_URL")
 
-TMP_DIR="$(mktemp -d)"
+CURRENT_SHA=$(sed -n 's#^.*https://github.com/tc39/source-map-tests/commit/\([0-9a-f]*\).*$#\1#p' "$README")
+
+if [ "$CURRENT_SHA" = "$SHA" ]; then
+  echo "Already up-to-date"
+  exit 0
+fi
 
 rm -rf "$TARGET_DIR"
 mkdir "$TARGET_DIR"