Revert "[PGO] Make emitted symbols hidden"

This reverts commit 4ea1a647.

This breaks on Darwin which tries to export these symbols
https://github.com/llvm/llvm-project/blob/ebb258d3b0785f6dcc65e1f277d0690891ddc94d/clang/lib/Driver/ToolChains/Darwin.cpp#L1363

I'll try to reland which that removed and approval from
Apple folks.