This commit fixes a small yet harmless issue that occurs when invoking
`ci_native_mpy_modules_build` on a persistent environment, as only X64
MPY files would be removed by the cleaning process.
Now the correct architecture is passed at all times when cleaning before
building a natmod for a particular architecture, forcing a full build of
all files to better simulate the CI environment (where there's no state
persisted between runs for this step).
Signed-off-by: Alessandro Gatti <a.gatti@frob.it>