Fixes#10539 in a diplomatic way (as opposed to telling Gentoo users
to just change their distro or rebuild zlib from upstream...).
(cherry picked from commit 67e6c1b735)
Godot-specific changes are undone in this commit, they will be readded
and properly documented in the following commit.
(cherry picked from commit 5681b7b60a)
Rémi Verschelde