This hack was removed during the libtool 2.2 upgrade.
The issue shows up as bundle builds failing to link libltdl/libltdlc.la
when they should in fact be linking ../libltdl/libltdlc.la in src/Makefile
It is caused by the macros of libtool 2.2 assuming the presence of
top_build_prefix but since autoconf 2.62 that was replaced with
ac_top_build_prefix and is no longer automatically defined in Makefile's.
Some distros also seem to have back-ported the removal of top_build_prefix
into their old autoconf causing macro version tests to fail.