Как задать MAKEOPTS только 1 пакету

MAKEOPTS="-j1"

Откуда такой параметр?

man portage

              package.env
                     Per-package environment variable settings. Entries refer to environment files that are placed in the /etc/portage/env/
                     directory and have the same format as make.conf(5).

                     Format:
                     - comment lines begin with # (no inline comments)
                     - one DEPEND atom per line followed by name(s) of environment file(s)

                     Example:
                     # use environment variables from /etc/portage/env/glibc.conf for the glibc package
                     sys-libs/glibc glibc.conf