gmp has DEPEND="~sys-devel/m4-1.4" sys-devel/m4-1.4.1 is out now, and gets built during emerge -UD world, only to get rolled back on the following emerge. is the ~ dep wrong, or it portage 2.0.50-r8 mishandling it?
dunno why you submitted it to me directly :)
it happens to me too... :(
changed depend to >=sys-devel/m4-1.4. Hope this works.