[Driver] Support Solaris/amd64 GetTls

This is the driver part of D91605 <https://reviews.llvm.org/D91605>, a
workaround to allow direct calls to `__tls_get_addr` on Solaris/amd64.

Tested on `amd64-pc-solaris2.11` and `sparcv9-sun-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D119829