tests: avoid '$MAKE' redirections, use 'run_make' instead

tests: avoid '$MAKE' redirections, use 'run_make' instead

The use 'run_make' with  the -E, -O and -M option, it is more
idiomatic now.  Also, this way, centralized fixes and improvements
done in 'run_make' will automatically propagate through most of
the testsuite.

* syntax-checks.mk (sc_tests_no_run_make_redirect): Also check against
'$MAKE' invocations that uses output redirections (and not only against
'run_make' invocation that do so).
* Several tests: Adjust (and few minor cosmetic changes as well, while
at it).

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>