[linker] fix armv7 & add aarch64

This adds Global Offset Table logic, as well as PLT like logic for armv7
and aarch64; which replaces the preexisting symbolExtras logic, by
placing the PLT tables next to the separtely loaded sections. This is
needed to ensure that the symbol stubs are in range.

Reviewers: bgamari, austin, erikd, simonmar

Reviewed By: bgamari

Subscribers: Ericson2314, ryantrinkle, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3448