Add relocation type R_X86_64_REX_GOTPCRELX

Add relocation type R_X86_64_REX_GOTPCRELX

Summary:
Adding support for the `R_X86_64_REX_GOTPCRELX` relocation type.
This relocation is treated by the linker the same as the `R_X86_64_GOTPCRELX` type
`G + GOT + A - P` to generate relative offsets to the GOT.
The `REX` prefix has no influence in this stage.

This is based on https://github.com/hjl-tools/x86-psABI/wiki/x86-64-psABI-r252.pdf

Test Plan: ./validate

Reviewers: erikd, austin, bgamari, simonmar

Reviewed By: erikd

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2303

GHC Trac Issues: #12147

Gbp-Pq: Name R_X86_64_REX_GOTPCRELX