simplify gcc_check/1
simplify gcc_check/1

The fix-point computation is no longer necessary: Instead, we
re-enable the queue after gcc_check has processed the list and leave
the fix-point computation to the constraint mechanism.

mndrix/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,koryonik/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel