lic2soc: factorize some Soc.gao tests

For the time being, we simple try to factorise out the test of
consecutive gao that holds on the same clock.

ps : also fix a pb (infinite loop in SortActions.topo_sort)
introduced in the previous change that, for a strange reason
(Makefile issue), was not catched by the test (almost all test were
failing !!).

pps : it actually seems to break quite a lot of test, but its my test
script that wrong ! since version 527 (we are 534), the compiler used
to perform the test in the tmp dirs is not upadated ! (well it is,
but on the wrong machine...).

I commit this change still as it introduces no more test failures.