Get rid of kmake_args(), just use _m_listKMakeArgs

Generator._m_listMakeOpts is never used without being concatenated to the
arguments generated by kmake_args(), so just consolidate the two lists in
_m_listKMakeArgs and get rid of both kmake_args() and _m_listMakeOpts.
Ignore exceptions when deleting temp files in Generator.__del__()

Logical follow-up to commit 6f2c909fd983de6d00b51fa676053dc6b6ccd873, now
I run into a situation when _m_sSrcIrfArchivePath has been correctly
initialized, but the corresponding file hasn’t been created yet.

This ignores exceptions from the above situation.