There are both powerpc and ppc64 architectures (as well as ppc64el), and I'm actually not sure what the difference is, because both the porterbox where I reproduced the problem (which is said to be a powerpc porterbox) and a ppc64 porterbox have the same uname -a output and binaries are "ELF 32-bit MSB shared object, PowerPC or cisco 4500, version 1 (SYSV)".
Linux partch 3.16.0-4-powerpc64 #1 SMP Debian 3.16.36-1+deb8u2 (2016-10-19) ppc64 GNU/Linux Linux pizzetti 3.16.0-4-powerpc64 #1 SMP Debian 3.16.36-1+deb8u2 (2016-10-19) ppc64 GNU/Linux Anyway, so the ABI is 32-bit (did you find the build log I linked to?).
