pyoxidizer: simplify targets
The split targets existed to enable the use of a non-default
distribution flavor on Windows. Modern versions of PyOxidizer
use the "standalone_dynamic" distribution flavor by default.
So our split brain workaround is no longer needed.
Here, we unify the targets. We also remove an unreferenced
target function to create a resources file.
Differential Revision: https://phab.mercurial-scm.org/D10681
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