pyoxidizer: use `legacy_windows_stdio` on Windows

The C executable sets this too, otherwise no output shows up (when paging?).
There is also `legacy_windows_fs_encoding`, but I'm not setting that for now
because the C executable doesn't either.

Differential Revision: https://phab.mercurial-scm.org/D8053

contrib/packaging/pyoxidizer.bzl

@@ -23,6 +23,7 b' def make_exe():'
         run_eval = code,
         # We need this to make resourceutil happy, since it looks for sys.frozen.
         sys_frozen = True,
+        legacy_windows_stdio = True,
     )
 
     exe = dist.to_python_executable(