[llvm] [PowerPC] Support local-dynamic TLS relocation on AIX (PR #66316)

[via llvm-commits]

stephenpeckham wrote:

The primary advantage of the local-dynamic access method is that you only make a single function call to __tls_get_mod() and use the returned pointer to get at all TLS variables.  This implementation makes a function call for every variable.  The only thing you've gained is a reduction in the number of TOC symbols.

https://github.com/llvm/llvm-project/pull/66316