misc/qubes-run-gnome-terminal: avoid external utility (grep)

Shave off a few milliseconds.

misc/qubes-run-gnome-terminal

@@ -5,8 +5,7 @@
 # Check if our gnome-terminal version supports --wait
 # (we can't just run it and check exit code, because if it works, it will
 # return the exit code of the child process)
-if gnome-terminal --help-terminal-options | grep --silent -- --wait; then
-    exec gnome-terminal --wait "$@"
-else
-    exec gnome-terminal "$@"
-fi
+case "$(gnome-terminal --help-terminal-options)" in
+    *--wait*) exec gnome-terminal --wait "$@" ;;
+    *)        exec gnome-terminal "$@" ;;
+esac