lint: warn against redirected 'run_make' invocations

lint: warn against redirected 'run_make' invocations

The testsuite shell function 'run_make()' has the three options
-E, -O and -M to perform the various kind of output redirections,
so the test scripts should use them instead of redirecting the
output "by hand":

    run_make ARGS >stdout           =>  run_make -O ARGS
    run_make ARGS >stderr           =>  run_make -E ARGS
    run_make ARGS >stdout 2>stderr  =>  run_make -O -E ARGS
    run_make ARGS >output 2>&1      =>  run_make -M ARGS

See the commit message of v1.13.2-13-gc7cfa09, 2013-05-22
(tests: run_make: options to do command redirection) for an
explanation of why this is a good idea.

It's worth noting that the present patch only introduced a new
static maintainer check looking against the undesired idioms,
but doesn't yet remove usages of such idioms from the testsuite.
That will be done by follow-up patch(es).

* syntax-checks.mk (sc_tests_no_run_make_redirect): New check.
(syntax_check_rules): List it.

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