mk: condense main() again

i prefer it this way. this reverses the change that
i made a few revisions ago

Signed-off-by: Leah Rowe <leah@libreboot.org>

mk

@@ -20,21 +20,13 @@ eval "`setvars "" vdir src_dirname srcdir mode`"
 
 main()
 {
-	cmd=""
-	if [ $# -gt 0 ]; then
-		cmd="$1"
-		shift 1
-	fi
+	cmd="" && [ $# -gt 0 ] && cmd="$1" && shift 1
 
 	case "$cmd" in
-	version)
-		printf "%s\nWebsite: %s\n" "$relname" "$projectsite" ;;
-	release|inject)
-		$cmd "$@" ;;
-	-*)
-		return 1 ;;
-	*)
-		$err "bad command" ;;
+	version) printf "%s\nWebsite: %s\n" "$relname" "$projectsite" ;;
+	release|inject) $cmd "$@" ;;
+	-*) return 1 ;;
+	*) $err "bad command" ;;
 	esac
 	set -u -e # some commands disable them. turn them on!
 }