Fix shellcheck warning

* build-aux/update-subdirs: Fix issue indicated by the shellcheck
linter (warning SC2046).

diff --git a/build-aux/update-subdirs b/build-aux/update-subdirs
index 336029fb71067d4ff85406e35ccc2d43a5dae103..96712f0b32e5a9b7e8e2c7a8cc81dcf527497b84 100755 (executable)
--- a/build-aux/update-subdirs
+++ b/build-aux/update-subdirs
@@ -26,7 +26,7 @@ for file in *; do
        *.elc | *.el | term | RCS | CVS | Old | . | .. | =* | *~ | *.orig | *.rej)
          ;;
        *)
-           if [ -d $file ]; then
+            if [ -d "$file" ]; then
                if [ "$file" = "obsolete" ]; then
                    subdirs="$subdirs \"$file\""
                else