Rip out runtime linker/compiler checks

We used to choose flags to pass to the toolchain at runtime based on the
platform running GHC, and in this commit we drop all of those runtime
linker checks

Ultimately, this represents a change in policy: We no longer adapt at
runtime to the toolchain being used, but rather make final decisions
about the toolchain used at /configure time/
(we have deleted Note [Run-time linker info] altogether!).

This works towards the goal of having all toolchain configuration logic
living in the same place, which facilities the work towards a
runtime-retargetable GHC (see #19877).

As of this commit, the runtime linker/compiler logic was moved to
autoconf, but soon it, and the rest of the existing toolchain
configuration logic, will live in the standalone ghc-toolchain program
(see !9263)

In particular, what used to be done at runtime is now as follows:
* The flags -Wl,--no-as-needed for needed shared libs are configured
  into settings
* The flag -fstack-check is configured into settings
* The check for broken tables-next-to-code was outdated
* We use the configured c compiler by default as the assembler program
* We drop `asmOpts` because we already configure -Qunused-arguments flag
  into settings (see !10589)

Fixes #23562

Co-author: Rodrigo Mesquita (@alt-romes)