fix loss of $Config{ccflags} on darwin

[tonycoz]

This skips some of the cleanup that EU::MM_Unix::cflags does, it might be better to have an extra_cflags()* method to add the -Wno-error=... instead of using cflags as the original commit did, but this Works For Me.

*or whatever name

[haarg]

This doesn't seem like the correct solution. I think the problem is the order. Other OS modules that override cflags call SUPER::cflags first before making their modifications.

[tonycoz]

@haarg 's #380 is better, so closing this one.