Are you doing the 32-bit build with OBJECT_MODE=64 environment setting ? (According to the perl source's README.aix, that would be wrong.)
I take it that the 64-bit build is fine ?
It's a bug in lib/ExtUtils/MM_aix.pm
If you make the alteration to lib/ExtUtils/MM_aix.pm as specified there, you should be successful.
Another option would be to build perl-5.30.0 or later.