Makefile.inc1: Rework ELF Tool Chain bootstrapping

[emaste]

Summary

Remove additional conditions and bootstrap elfctl, elfdump, and elfcopy
(aka objdump) if ELFTOOLCHAIN_BOOTSTRAP is true.  The first two are
bespoke tools that won't exist in an external GNU or LLVM binutils, and
elfcopy is also not provided by that name.

This should fix GCC CI builds, which was skipping the elfcopy build
because of the ${TARGET_ARCH} != ${MACHINE_ARCH} condition.

Reported by:    olce
Fixes: b885643b63e4 ("boot: Always use ELF Tool Chain elfcopy for EFI builds")
Sponsored by:   The FreeBSD Foundation

[emaste]

Changes to this section over time include:

• rG:0163af236079a
• rG:2bf36e7e089fe
• rG:31942939034ec
• rG:7d612a433e65d
• rG:27051ca14b0bf
• rG:a8bed44af5ede
• rG:1bc28ffccda2c
• rG:a8bed44af5ede
• rG:084748985d519
• rG:c1da297433fb5
• rG:9b844631a61b2
• rG:c6081dea597a4
• rG:9b135747a3260

[emaste]

Cirrus-CI test run: https://cirrus-ci.com/build/5750132458651648

[brooks]

Seems fine conceptually, a couple comments.

Makefile.inc1

2914

I wonder if this comment should mention elfctl since it has other uses (I should bring over ELF_FEATURES from CheriBSD).

2922

I wonder if we should change this guard (maybe ${XNM}) given that we don't actually use AS any more.

[emaste]

Update comments per @brooks, use XNM instead of XAS

[emaste]

Makefile.inc1

2915