Fix various minor issues with Gentoo; make CI pass

This patch contains the known set of changes needed to make a gentoo
image build successfully.

- Standardize use of GENTOO_EMERGE_DEFAULT_OPTS, reduce duplication of
  options set there.
- Correct the cleanup commands to reflect standard Gentoo good
  practices by omitting --complete-graph, which is unneeded with --deep,
  and using --changed-use instead of --newuse to reduce unneeded package
  churn.
- Stop using deprecated layman command to manage reposiotry overlays,
  instead use new supported eselect-repository
- Set new USE flags required for LVM and installkernel. This was
  communicated via a Gentoo news item and is a required cleanup.
- Remove now-invalid skip of gpg if using musl

This is the set of changes needed to get the CI job passing and make DIB
build images at all, and we'd like to land them, but there are still
items we'd like to complete to enhance Gentoo support in DIB:
- Optional, built-in support for Gentoo binhosts -- where you can set a
  DIB_GENTOO_BINHOST=true (or similar) and have the binhost enabled by
  default.
- Make the default configuration of EMERGE_DEFAULT_OPTS more easily
  managed in a DIB-style manner, e.g. setting --quiet vs --verbose based
  on the value of DIB_DEBUG_TRACE.

Signed-Off-By: Jay Faulkner <jay@jvf.cc>
Signed-Off-By: Sam James <sam@gentoo.org>
Co-Authored-By: Sam James <sam@gentoo.org>
Change-Id: Idab82a9fa986fcc56fe4e1e1bf0445c7306b2858

diskimage_builder/elements/gentoo/bin/install-packages

@@ -20,6 +20,12 @@ fi
 set -eu
 set -o pipefail
 
+# note(JayF): YACC and LEX are both set by gentoo alternatives handling if you want to
+#             use alternative implementations of them. Since whatever alternative
+#             implementation is opted-for may not availabe inside the image, we need to 
+#             unset the environment to ensure default behavior.
+unset YACC LEX
+
 # env is not sourced with user specified package inclusions
 # set the default bash array if GENTOO_EMERGE_ENV is not defined as an array
 if ! declare -p GENTOO_EMERGE_ENV  2> /dev/null | grep -q '^declare \-a'; then
@@ -36,7 +42,7 @@ for (( i=0; i<${#GENTOO_EMERGE_ENV[@]}; i++ )); do
     eval export "${GENTOO_EMERGE_ENV[i]}"
 done
 # set default opts
-GENTOO_EMERGE_DEFAULT_OPTS=${GENTOO_EMERGE_DEFAULT_OPTS:-"--binpkg-respect-use --rebuilt-binaries=y --usepkg=y --with-bdeps=y --binpkg-changed-deps=y --quiet --jobs=2 --autounmask=n"}
+GENTOO_EMERGE_DEFAULT_OPTS=${GENTOO_EMERGE_DEFAULT_OPTS:-"--binpkg-respect-use --rebuilt-binaries=y --usepkg=y --with-bdeps=y --binpkg-changed-deps=y --jobs=2 --verbose --autounmask=n"}
 
 ACTION='install'
 
@@ -76,7 +82,7 @@ while true; do
             if [[ ! -f ${PORTDIR}/profiles ]]; then
                 emerge-webrsync -q
             fi
-            install_gentoo_packages --update --deep --newuse --complete-graph=y @world
+            install_gentoo_packages --update --deep --changed-use @world
             install_gentoo_packages --verbose=n --depclean
             install_gentoo_packages --usepkg=n @preserved-rebuild
             etc-update --automode -5
@@ -121,7 +127,7 @@ else
         if [[ ! -f ${PORTDIR}/profiles ]]; then
             emerge-webrsync -q
         fi
-        install_gentoo_packages -q --jobs=2 --changed-use "${PKGS}"
+        install_gentoo_packages --changed-use "${PKGS}"
     elif [[ "${ACTION}" == 'remove' ]]; then
         if [[ ! -f ${PORTDIR}/profiles ]]; then
             emerge-webrsync -q
@@ -143,3 +149,4 @@ else
         echo 'something went really wrong, install action is not install or remove'
     fi
 fi
+

diskimage_builder/elements/gentoo/finalise.d/99-cleanup

@@ -18,7 +18,7 @@ fi
 [[ ! -e ${PORTDIR}/profiles ]] && emerge-webrsync
 
 # make world consistent
-emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --complete-graph=y --update --newuse --deep @world
+emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --update --changed-use --deep @world
 # rebuild packages that might need it
 emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --usepkg=n @preserved-rebuild
 # remove unneeded packages

diskimage_builder/elements/gentoo/pre-install.d/02-gentoo-02-flags

@@ -19,7 +19,8 @@ mkdir -p /etc/portage/package.use
 # needed in order to install pip packages as root
 echo 'dev-python/pip vanilla' >> /etc/portage/package.use/pip
 # needed to create disk images
-echo 'sys-fs/lvm2 -thin' >> /etc/portage/package.use/grub
+echo 'sys-fs/lvm2 lvm -thin' >> /etc/portage/package.use/grub
+echo 'sys-kernel/installkernel dracut' >> /etc/portage/package.use/kernel
 echo 'sys-boot/grub device-mapper' >> /etc/portage/package.use/grub
 echo 'sys-boot/grub grub_platforms_efi-64' >> /etc/portage/package.use/grub  # always enable efi-64
 if [[ 'amd64' == "${ARCH}" ]]; then
@@ -36,6 +37,5 @@ echo "~sys-block/open-isns-0.101 ~${ARCH}" >> /etc/portage/package.accept_keywor
 
 # musl only valid for amd64 for now
 if [[ "${GENTOO_PROFILE}" == *"musl"* ]]; then
-    echo "dev-vcs/git -gpg" >> /etc/portage/package.use/musl  # gpg doesn't build on musl profiles
     echo "sys-libs/pam cracklib" >> /etc/portage/package.use/musl
 fi

diskimage_builder/elements/gentoo/pre-install.d/02-gentoo-03-enable-overlays

@@ -20,16 +20,11 @@ if [[ ${GENTOO_OVERLAYS} != '' ]]; then
     fi
 
     emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --oneshot openssl openssh
-    # install layman
-    emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --deep --ignore-built-slot-operator-deps=y layman
-    # set layman config options
-    sed -i 's/^check_official.*/check_official : No/g' /etc/layman/layman.cfg # allow unoffical repos
-    # sync the initial overlay list
-    layman -S
+    emerge ${GENTOO_EMERGE_DEFAULT_OPTS} --oneshot eselect-repository
     # enable the various overlays, ignore failures (overlay my already be enabled)
     set +e
     for OVERLAY in ${GENTOO_OVERLAYS}; do
-        layman -a "${OVERLAY}"
+        eselect repository enable "${OVERLAY}"
     done
     set -e