cmTarget: Restore Fortran_PREPROCESS property initialization

Fix a typo from commit e522f8ca06 (cmTarget: factor out properties
initialized for target which compile, 2023-02-01, v3.27.0-rc1~577^2~13),
that broke this property.

Also update the test suite to use this upgrade as some level of
coverage.

Fixes: #25123
2 files changed