Looks generally OK. A few potential clean-ups:
I think it will keep everyone saner in the long run if canonical variables
like srcdir have their canonical meanings everywhere. So if you really
need them to use an absolute directory name, then make them use abs_srcdir
as the variable name for that.
Rather than various numbers of ../ prefixes, perhaps it would become easier
to read and to maintain if all those were rewritten in terms of builddir
and/or top_builddir (i.e. $top_builddir/src/readelf, etc.).