stage1: fix cmake regression

- add `None` as a valid CMAKE_BUILD_TYPE
- this is a legitimate setting used by packagers

regression was caused by c6df5deb3450e0d8a2ba449c34a0bd195fbce8ec
d0a9da74efMichael Dusan committed on 2/5/2020, 1:24:50 PMparent25cbee0
1 file changedLine totals unavailable