root@Host /usr/src/linux # emerge --ask dev-util/rustup -q

 * IMPORTANT: 8 news items need reading for repository 'gentoo'.
 * Use eselect news read to view new items.


!!! All ebuilds that could satisfy "dev-util/rustup" have been masked.
!!! One of the following masked packages is required to complete your request:
- dev-util/rustup-9999::gentoo (masked by: missing keyword)
- dev-util/rustup-1.25.1-r1::gentoo (masked by: ~amd64 keyword)

For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.