tools/runqslower: Use Makefile.include

Makefile.include defines variables such as OUTPUT and CC for out-of-tree
build and cross-build. Include it into the runqslower Makefile and use
its $(QUIET*) helpers.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201110164310.2600671-5-jean-philippe@linaro.org