This CPU doesn't support some built-in fucntions but it tries to build it with Upstream issue: github[\.]com/simdjson/simdjson/issues/2319 (sorry my account is new so I had to remove the URL)
Even there's a checker github[\.]com/simdjson/simdjson/blob/7712ecf164563a3703803c9b1b85a3154921700d/include/simdjson/portability.h#L51 github[\.]com/simdjson/simdjson/blob/7712ecf164563a3703803c9b1b85a3154921700d/include/simdjson/implementation_detection.h#L107 Gentoo ebuild enable `SIMDJSON_IMPLEMENTATION_PPC64` by force. So it fails on this machine.