Why has been support for libressl removed from squid-4.10? Removal of libressl support is only difference between squid-4.9.ebuild and squid-4.10.ebuild. I compiled squid.4.10 with libressl and it's working fine without any errors.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=c6378bfed30f088333db2b69eeeb7d77cef5d3f8
4.10 effectively dropped libressl support, i.e. they give no chance it gonna work if it is even was compiled successfully. http://www.squid-cache.org/Versions/v4/squid-4.10-RELEASENOTES.html#toc1.1
Martin, it would be best to ask upstream about this. Maybe try the squid mailing list or their bug tracking. I'm sure we'll add libressl support in Gentoo if it's supported upstream.