math/R: Fix build issues when LIBR option is off and fix runtime issue by
permitting FLANG only with RBLAS
- Only apply SONAME patches when the relevant options are chosen. This prevents install errors when LIBR is off.
- Only permit the FLANG option when RBLAS is chosen, because FLANG causes some configure-time checks to fail and the shared RBLAS library is fallen back upon, but not properly packaged, which causes runtime issues.
- Bump PORTREVISION
Reported by: firstname.lastname@example.org
Differential Revision: https://reviews.freebsd.org/D11726