Update recipe for flang-aarch64 slaves

- Update compiler location for flang-aarch64-ubuntu-{clang and gcc10}
- Add another email to the extra recipient for flang-aarch64
- Make flang-aarch64 slaves build new flang driver by default
- Add a missing coma to flang-aarch64-ubuntu-gcc10 recipe

Differential Revision: https://reviews.llvm.org/D87125
2 files changed