The 5.11 kernel is out

FWIW, GNU make assumes all makefiles are UTF-8-encoded, insofar as that matters, and does recognize (and ignore) the UTF-8 BOM. Although the BOM can't be "somewhere in there"; it has to be the first 3 chars of a file of course.

GNU make doesn't reject invalid UTF-8 chars though, and it doesn't reject makefiles that declare they are not UTF-8: any 3 chars that are not a UTF-8 BOM are interpreted as Makefile content.

Probably that should be addressed and a warning generated if the first 3 chars are determined to be a non-UTF-8 BOM.