Update: Add pinephone build mode and fix build setting inconsistencies encountered.

Update: Add pinephone build mode and fix build setting inconsistencies encountered.

Add a convenience build mode similar to the `android` build mode for the `pinephone`.
Just like with the `android` build mode, add a parameter to build using the `pinephone` mode to the `bootstrap-example.sh` script.
Utilize the android build variables for the script, replacing them with a more generic variable name.

I discovered and addressed some build settings inconsistencies while mass adding the `pinephone` mode.