branches: 1.2.2; 1.2.4;
tests/libexec/ld.elf_so: Fix helper library makefiles.

1. Consolidate logic into a single helper.mk to reduce duplication.
2. Set NO* variables, not MK* variables which are reserved for user.
3. Avoid eager X!= in favour of lazy ${X:sh}.
4. Mark _g.a set list entries obsolete. Never should've been built!

PR misc/57462

ld.elf_so: Test another edge case of mismatched TLS models.

One library defines a symbol and _doesn't_ use it, so it has no
indication of whether the symbol is for static TLS or dynamic TLS,
and then two other libraries use it in different ways.

XXX pullup-10

branches: 1.1.2; 1.1.4;
ld.elf_so: Test another edge case of mismatched TLS models.

One library defines a symbol and _doesn't_ use it, so it has no
indication of whether the symbol is for static TLS or dynamic TLS,
and then two other libraries use it in different ways.

XXX pullup-10