Restore ${OBJDUMP}

[brooks]

Summary

Define an OBJDUMP variable and prefer the cross tools version where
available. Allow XOBJDUMP to override and search for llvm-objdump in
CROSS_BINUTILS_PREFIX to maximize our chances of finding one.

A future commit will use objdump to compare the set of symbols built in
libraries with a reference list.

This reverts commit fd406aa3de47e89456febcaf6cb65d22a6317bc1

[emaste]

A future commit will use objdump to compare the set of symbols built in libraries with a reference list.

No objection, but is there a reason we cannot use nm and/or readelf?

[brooks]

In D44275#1013228, @emaste wrote:

A future commit will use objdump to compare the set of symbols built in libraries with a reference list.

No objection, but is there a reason we cannot use nm and/or readelf?

I thought of objdump first. :) After a recent NetBSD post of someone doing something similar with nm I looked at it and nm flags are a portability nightmare (see my follow up email). readelf also has issues (llvm-readelf lacks --use-dynamic), but looking it over I think things might better than using objdump. I'll see about switching to readelf.

[brooks]

I'm going to switch to using readelf