From: Justin M. Forbes on
gitlab.com
https://gitlab.com/cki-project/kernel-ark/-/merge_requests/2370#note_1319...
@mh21
```
ifndef RHJOBS
RHJOBS=$(shell j=$$(echo $(MAKEFLAGS) | grep -Eo "(^|[ ])-j[0-9]*" | xargs
); \
if [ -z "$${j}" ]; then \
echo "1"; \
else \
j=$$(echo "$${j}" | tr -d "\-j"); \
[ -z "$${j}" ] && nproc --all || echo $${j}; \
fi)
endif
```