[AIX]Generate debug info for static init related functions

Set the debug location for static init related functions(__dtor
and __finalize) so we can generate valid debug info on AIX by invoking
-g with clang or -debug-info-kind=limited with clang_cc1.

This also works for any other future targets who may use sinit and
sterm functions for static initialization, where a direct call to
dtor will be generated within finalize function body.

This patch also aims at validating that the debug info generated
is correct for AIX sinit related functions.

Differential Revision: https://reviews.llvm.org/D83702