build: format-check: invoke `make` in a portable way
build: format-check: invoke `make` in a portable way

I've added `uncrustify` to my build environment, and as a result the
build started failing for me because it tried to invoke `make
format-check`. I use the ninja generator for CMake, which means that
there's no `Makefile` generated in my build directory.

Fix this by invoking the relevant target via CMake.

sysrepo/sysrepo,sysrepo/sysrepo,sysrepo/sysrepo