[clang] [flang] [llvm] [flang][cmake][perf-training] Optimize flang with PGO and BOLT (PR #198863)

[Michael Kruse via cfe-commits]

https://github.com/Meinersbur commented:

Consider the new coding standard for documentation: #197666

Needs rebasing to #171515. `%flang_fc1` new requires `-fintrinsic-modules-path` to find its modules.

https://github.com/llvm/llvm-project/pull/198863