[CIR] Do not assume function aliases are dso_local under PIC (#234753)
For PIC code that is not a PIE, shouldAssumeDSOLocal marks a function
dso_local when it can use a local alias, as classic codegen does.
Classic applies that only to real functions, never to aliases. CIR
represents a function alias as a FuncOp with an aliasee, so the check
now skips aliases. The flag does not reach LLVM IR yet, because MLIR's
translation drops dso_local on aliases. #234012 fixes that.
Assisted-by: Cursor / claude-opus-5.5