I've missed this while reviewing 6db6190002.
I only built big endian ppc64, so that didn't occur to me.
From meson manual:
> Those porting from autotools should note that Meson does not add
> endianness to the name of the cpu_family. For example, autotools will
> call little endian PPC64 "ppc64le", Meson will not, you must also check
> the .endian() value of the machine for this information.
This code should handle that correctly.