Ignore dependencies on upgrade and remove excess packages

There are new dependencies from elfutils and binutils which needs to be
removed from the container. So we clean any packages not found in the
buildinfo from the chroot.

Signed-off-by: Morten Linderud <morten@linderud.pw>

Author: Foxboron

repro.in

@@ -262,7 +262,14 @@ __END__
     msg "Installing packages"
     # shellcheck disable=SC2086
     exec_nspawn build --bind="$(readlink -e ${cachedir}):/cache" bash -c \
-        'yes y | pacman -U --overwrite "*" -- "$@"' -bash "${packages[@]}"
+        'yes y | pacman -Udd --overwrite "*" -- "$@"' -bash "${packages[@]}"
+
+    read -r -a buildinfo_packages <<< "$(buildinfo -f installed "${pkg}")"
+    uninstall=$(comm -13 \
+        <(printf '%s\n' "${buildinfo_packages[@]}" | rev | cut -d- -f4- | rev | sort) \
+        <(exec_nspawn build --bind="$(readlink -e ${cachedir}):/cache" pacman -Qq))
+
+    exec_nspawn build pacman -Rdd --noconfirm -- $uninstall
 
     build_package "build" "$builddir"
     remove_snapshot "build"