Not really understanding your question. Are you cross compiling on an x86 for pi4 aarc64 or cross compiling on your pi4 for a 32 bit kernel.
After thought:
It has been a while but if I remember right there was some warnings I believe cross compiled on a x86 for pi4 aarch64 that can be ignored. Cross compiling on x86 for 32 bit did not have any warnings. Of course I could have that backwards. Usually warnings can be ignored.
Are you following what I posted here:
https://forum.manjaro.org/t/wiki-how-to-contribute-to-manjaro-arm/35461/58