Debian10 support

It's not possible to build this project under Debian10. The reason is that FindKernelHeaders.cmake was developed for RHEL-based. In Debian kernel-headers are located in two folders: /usr/src/linux-headers-- AND /usr/src/linux-headers--common

This Makefile works fine:

obj-m += hello.o

all:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

/lib/modules/4.19.0-6-amd64/build/Makefile contains this:

MAKEARGS := -C /usr/src/linux-headers-4.19.0-6-common O=/usr/src/linux-headers-4.19.0-6-amd64