Update the preprocessor regression tests to use the new driver if the new driver is built (FLANG_BUILD_NEW_DRIVER=On), otherwise the tests will still run using f18.
Summary of changes:
- Introduce %flang to the regression tests, which points to the new driver if it is built or otherwise points to f18
- Update all tests in flang/test/Preprocessing/ to use %flang
Differential Revision: https://reviews.llvm.org/D94805
When an illegal character appears in Fortran source (after
preprocessing), catch and report it in the prescanning phase
rather than leaving it for the parser to cope with.
Differential Revision: https://reviews.llvm.org/D86553