[compiler-rt] [compiler-rt] Use mangled function names on ARM64EC (PR #137960)

[Jacek Caban via llvm-commits]

cjacek wrote:

> I wonder if there is a way to unify `SYMBOL_IS_FUNC` and `FUNC_SYMBOL`. We have a number of different places where we indicate that a label is a function, and it seems it would be very confusing for most to know which one belongs where.

Thanks for the reviews. The best I could come up with is renaming `SYMBOL_IS_FUNC` to `DEFINE_FUNC_SYMBOL`. That name seems more accurate, especially if we move the `.globl` directive into the macro as well. What do you think? Should I go ahead with that?

https://github.com/llvm/llvm-project/pull/137960