Support uftrace (and other fentry consumers)

[lu-zero]

uftrace should work already with -Zprofile but seems it is not.

Related issues

• LLVM instrument functions
• -Zprofile tracking issue

[quark-zju]

I think -Zprofile does a different thing - similar to gcc --coverage, not gcc -pg.

#57220 adds another flag for uftrace support.

[lu-zero]

It would need probably some documentation somewhere now.