Remove perror from ld_assemble, ld_compile and ld_nm
ERROR should really be reserved for errors in the testsuite framework,
not just normal errors from the tools under test. Removing use of
perror has been suggested before but without action, over concerns
that some test failures might be missed. This patch removes uses of
perror in ld_assemble, ld_compile and ld_nm, and updates numerous
places that ignored the result of these functions by inappropriately
returning an "unresolved" test status. Net result over my large set
of targets look good, in some cases improving the diagnostics, eg: