[compiler-rt][profile][AIX] pass extra link opts for test

The AIX linker doesn't export any symbols by default, so an export list is usually used. Since clang doesn't have the tools to auto-generate an export list yet, just pass the linker an extra opt to tell it to export everything. This is  generally not recommended for real shared libs, but is fine for the purpose of this test.

Differential Revision: https://reviews.llvm.org/D118101