[cmake] Always run native build standalone
This ensure 2 goals:
- The cross compilation and regular build take the same codepath, which ensure it is more used and therefore will stay robust.
- The native executables can have different build options that generated ones.
- Do a native compilation using cmake
- Cross compile for ARM
Both are green.
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D5001