Separate base packages from customizations

The `build.packages` and `install.packages` files in the CONFIGDIR now
only need to include *additional* packages to install.  The packages
*required* for Aimee OS are always installed, listed in the
corresponding files in the source directory.

build-rootfs.sh

@@ -21,15 +21,21 @@ ln -snf \
     /var/db/repos/gentoo/profiles/${profile} \
     /mnt/gentoo/etc/portage/make.profile
 
-ROOT=/mnt/gentoo \
-PORTAGE_CONFIGROOT="${CONFIGDIR}"/portage/target \
-< "${CONFIGDIR}"/install.packages xargs -ro \
-${target}-emerge -KvnuUDj --rebuilt-binaries=y
+cat \
+    install.packages \
+    "${CONFIGDIR}"/install.packages \
+    | xargs -ro \
+${target}-emerge \
+    --root=/mnt/gentoo \
+    --config-root="${CONFIGDIR}"/portage/target \
+    -KvnuUDj \
+    --rebuilt-binaries=y
 
-ROOT=/mnt/gentoo \
-PORTAGE_CONFIGROOT="${CONFIGDIR}"/portage/target \
 < "${CONFIGDIR}"/installonly.packages xargs -ro \
-${target}-emerge -vnuUDj
+${target}-emerge \
+    --root=/mnt/gentoo \
+    --config-root="${CONFIGDIR}"/portage/target \
+    -vnuUDj
 
 ROOT=/mnt/gentoo \
 locale-gen