add info how to force rebuild

README.md

@@ -5,12 +5,12 @@
 to build an application
 
 1. modify the example minimal application source code found in 
-```bash
+```sh
 vim ./apk/Makefile 
 vim ./apk/..... (other files)
 ```
 2. run the compilation in the container (which is build via `Dockerfile` and `docker-compose.yml` upon first usage)
-```bash
+```sh
 docker-compose run compile
 ```
 
@@ -38,4 +38,13 @@ to build an Android application, that via its "Hello World" app example should a
 - being portable and easily installable (hence the `docker compose`)
 - reuse Makefile as an often familiar concept of "recipe" way to build the application 
 
+## Helpful commands
+
+* coerce rebuild:
+```sh
+docker-compose down --remove-orphans --rmi all 
+docker-compose build --no-cache
+```
+
+