pyrex hardcodes MACOSX_DEPLOYMENT_TARGET to 10.3

[harry@…]

In Mac/DarwinSystem.py there's a line that does this:

os.environMACOSX_DEPLOYMENT_TARGET? = "10.3"

Which cases builds on Leopard to fail like this:

distutils.errors.DistutilsPlatformError: $MACOSX_DEPLOYMENT_TARGET mismatch: now "10.3" but "10.5" during configure