make shellcheck 0.9.0-1 more happy

tests/cwd-directory-not-accessible-by-unshared-user

@@ -11,12 +11,12 @@ mkdir /tmp/debian-chroot
 chmod 700 /tmp/debian-chroot
 chown user:user /tmp/debian-chroot
 if [ "{{ CMD }}" = "./mmdebstrap" ]; then
-	CMD=$(realpath --canonicalize-existing ./mmdebstrap)
+	set -- "$(realpath --canonicalize-existing ./mmdebstrap)"
 elif [ "{{ CMD }}" = "perl -MDevel::Cover=-silent,-nogcov ./mmdebstrap" ]; then
-	CMD="perl -MDevel::Cover=-silent,-nogcov $(realpath --canonicalize-existing ./mmdebstrap)"
+	set -- perl -MDevel::Cover=-silent,-nogcov "$(realpath --canonicalize-existing ./mmdebstrap)"
 else
-	CMD="{{ CMD }}"
+	set -- {{ CMD }}
 fi
-env --chdir=/tmp/debian-chroot runuser -u user -- $CMD --mode=unshare --variant=apt {{ DIST }} /tmp/debian-chroot.tar {{ MIRROR }}
+env --chdir=/tmp/debian-chroot runuser -u user -- "$@" --mode=unshare --variant=apt {{ DIST }} /tmp/debian-chroot.tar {{ MIRROR }}
 tar -tf /tmp/debian-chroot.tar | sort | diff -u tar1.txt -
 rm /tmp/debian-chroot.tar