Hi Michał,
i am attaching my complete build.log.

My USE flags are:

net-dns/unbound-1.6.2::gentoo [1.6.0::gentoo] USE="dnscrypt%* ecdsa gost python threads -debug -dnstap -libressl (-selinux) -static-libs -systemd% {-test}" ABI_X86="32 (64) (-x32)" PYTHON_TARGETS="python2_7" 5.253 KiB

dev-libs/libsodium-1.0.12:0/18::gentoo  USE="asm urandom -minimal -static-libs" CPU_FLAGS_X86="aes sse4_1" 0 KiB

Conrad