boot: Lift linker requirements

boot: Lift linker requirements

The biggest reason for forcing bfd was the use of linker scrips. Since
we don't rely on those anymore we can lift the requirement.

The biggest issue is gold as it does not understand -static-pie. Given
that it's pretty much on life support it's safe to just declare it not
supported anymore.

Don't link addons with libefi as clang/lld is sometimes very eager to
include memset etc., causing needless binary bloat and link errors with
LTO.

Fixes: #29165