Although the majority of OpenPOWER ELF V2 ABI use is on Little Endian, it is fully specified and is used in Big Endian mode as well.
As such, the correct detection of an ELFv2 system is via the _CALL_ELF preprocessor define, not the endianness.
This fixes JIT crashes on:
FreeBSD PowerPC64 ELFv2 variant (an experimental build)
on systems such as the Raptor Computing Systems TALOS II.
Original bug report at https://bugs.exim.org/show_bug.cgi?id=2353