RepoMan scours the neighborhood... dependency.bad 4 dev-libs/libusbx/libusbx-1.0.17.ebuild: DEPEND: ~amd64(hardened/linux/amd64) ['>=virtual/udev-200[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_x86_32(-)?,abi_x86_64(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?]'] dev-libs/libusbx/libusbx-1.0.17.ebuild: RDEPEND: ~amd64(hardened/linux/amd64) ['>=virtual/udev-200[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_x86_32(-)?,abi_x86_64(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?]'] dev-libs/libusbx/libusbx-1.0.17.ebuild: DEPEND: ~amd64(hardened/linux/amd64/selinux) ['>=virtual/udev-200[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_x86_32(-)?,abi_x86_64(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?]'] dev-libs/libusbx/libusbx-1.0.17.ebuild: RDEPEND: ~amd64(hardened/linux/amd64/selinux) ['>=virtual/udev-200[abi_x86_32(-)?,abi_x86_64(-)?,abi_x86_x32(-)?,abi_x86_32(-)?,abi_x86_64(-)?,abi_mips_n32(-)?,abi_mips_n64(-)?,abi_mips_o32(-)?]']
mgorny: Looks like the package.use.mask in hardened/linux/amd64/ you put broke multiple dependencies, see also bug 485810 and bug 485812 and bug 485814 ... there could be more too.
Added the listed packages to the mask, thanks. Also, moved the masks to package.stable.use.mask to defer the issues from happening :).