[llvm][AArch64] In case of LTO functions loose protection flags.

[DanielKristofKiss]

sign-return-address and similar module attributes should be propagated to
the function level before got merged because module flags may contradict and
this information is not recoverable.
Resulting the function is generated without the required protections.

[DanielKristofKiss]

/cherry-pick ded5de1

[DanielKristofKiss]

#80640 solves this issue on the main branch.

[llvmbot]

/pull-request #84039