To compile sucessfully with USE="-ssl" x11-misc/x11vnc should depend on net-libs/libvncserver also being compiled with USE="-ssl". This dependency on libvncserver's USE-flag isn't written yet. Many thanks for adapting it.
Already requested: https://github.com/gentoo/gentoo/pull/2548
Well I meant x11nvc-0.9.14.ebuild to contain RDEPEND=">=libvncserver-0.9.8[ssl=]" in order to compile properly if USE="-ssl" is set. Today the ebuild only contains RDEPEND=">=libvncserver-0.9.8"