maintcheck: whitelist some false positives Instead of tweaking or dumbing down some of our sources or tests in order not to make them spuriously trigger few maintainer checks, we tweak such checks instead. * syntax-checks.mk (sc_tests_overriding_macros_on_cmdline): Also allow the variable 'exp' to be overridden on the make command line. Whitelist the test 'make-dryrun.test' where appropriate. (sc_mkinstalldirs): When whitelisting the 'mkinstalldirs' occurrence in 'lib/Makefile.am', do not look for the exact line number: it is obviously too fragile.