I performed an ego sync, got the latest ebuild and attempted to update my system.  I am now getting this error.
emerge: there are no ebuilds to satisfy "dev-libs/libsodium[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?,abi_ppc_32(-)?,abi_ppc_64(-)?,abi_s390_32(-)?,abi_s390_64(-)?]"
 

Prior to the ebuild update, I was able to build the same version of unbound with dnscrypt enabled.