build: add twrp and twrp usage

build.sh

@@ -22,6 +22,7 @@ flags:
 
 commands:
     bootimage       build boot.img (kernel + dt.img + ramdisk, fast gate)
+    twrp	    build TWRP recovery.img
     bacon           full build -> lineage_rubenslte-*.zip
     clean           mka clean
     prune           remove all of "$BUILD"
@@ -73,8 +74,8 @@ do_build() {
 
     rlte_print "Commencing build (command: $CMD)"
 
-    if [ "$CMD" = "recoveryimage" ]; then
-	WITH_TWRP=true mka "$CMD"
+    if [ "$CMD" = "twrp" ]; then
+	WITH_TWRP=true mka recoveryimage
     else
 	mka "$CMD"
     fi
@@ -93,7 +94,7 @@ done
 shift $((OPTIND - 1))
 
 case "${1:-}" in
-    bootimage|recoveryimage|bacon|clean) CMD="${1:-}"; do_build ;;
+    bootimage|twrp|bacon|clean) CMD="${1:-}"; do_build ;;
     prune) rm -rf "$BUILD" ;;
     *) usage; exit 1 ;;
 esac