[AIX][pg] Add Correct Search Paths for Profiled Libraries

On AIX, profiled system libraries are stored at `/lib/profiled` and
`/usr/lib/profiled`. When compiling with `-pg`, we want to link against
libraries in those directories. This PR modifies the AIX toolchain to
add those directories to the linker search paths.

Differential Review: https://reviews.llvm.org/D137375