makefile: go back to using nitc (prevents file related sigv)

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests: adds some custom tests

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
makefile: fix "tests" rule

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>