[clang] [flang] [flang] Enable alias tags pass by default (PR #73111)

[Tom Eccles via cfe-commits]

tblah wrote:

> Thank you for the changes, Tom!
> 
> I have one minor comment, but I would like to ask to merge this after US holidays, if possible. Could you please postpone the merging until Monday GMT?

Sure. I'll wait until Monday.

https://github.com/llvm/llvm-project/pull/73111