Link zlib statically with bootloader on AIX.
On AIX zlib is an optional library found in
  /opt/freeware/lib
We link it statically so the bootloader can run on AIX machines with no
libz installed.
AIX does not have objdump command.
Also find shared objects not in library archives on AIX.
During the dependency analysis, we must also match shared objects that
are not embedded in a an library archive. This means we now match
libraries of both these forms:
* 'archivelib.a(objectmember.so/.o)'
* 'sharedlib.so'
An example of the second form is 'libz.so' which was not previously
picked up so the resulting program could not run on an AIX machine
without 'libz' installed.
Removed 'objdump' from requirements for AIX and FreeBSD.