Improve handling of circular dependencies

Several packages end up with circular dependencies, depending on which
Portage profile is selected.  The default profiles have a circular
dependency between *sys-libs/pam* and *sys-libs/libcap*.  Systemd and
SELinux profiles have even more issues.

We can break the circular dependencies by explicitly building *libcap*
with`USE=-pam` first, which happens to be the default configuration
generated by `crossdev`.  Then, we need to switch to a more complete
profile in order to build *glibc* and *util-linux*.  At this point, the
build root should be complete enough to build anything without circular
dependencies.

.gitignore

@@ -1,5 +1,6 @@
 /images
 /linux
 /output
+/.built
 /.prepared
 /.host-tools

build.sh

@@ -5,10 +5,7 @@ set -e
 
 . ./config
 
-USE=-pam \
+${target}-emerge -vuUDj sys-apps/util-linux
-${target}-emerge -1nvj --nodeps sys-libs/libcap
-USE='-cramfs -ncurses -nls -pam -readline -su -suid -systemd -udev' \
-${target}-emerge -1nvj --nodeps sys-apps/util-linux
 
 ${target}-emerge -vnuUDj \
     net-misc/openssh \

config-portage.sh

@@ -7,3 +7,8 @@ set -e
 
 cp -r host-portage/. /etc/portage/
 cp -r portage/. /usr/${target}/etc/portage/
+
+# Set the Portage profile
+ln -snf \
+    /var/db/repos/gentoo/profiles/${profile} \
+    /usr/${target}/etc/portage/make.profile

prepare.sh

@@ -10,14 +10,26 @@ if [ ! -f /var/db/repos/gentoo/metadata/timestamp ]; then
     emerge-webrsync
 fi
 
-# Migrate to the merged-usr layout
+ARCH=$(PORTAGE_CONFIGROOT=/usr/${target} portageq envvar ARCH)
-mkdir -p /usr/${target}/bin
+
-emerge -bknv --quiet-build=y merge-usr
+
-merge-usr --root=/usr/${target}
+# For some reason, libcap installs its pkg-config files in the wrong
+# place.  More strangely, even though `PKG_CONFIG_PATH` contains that
+# directory, `pkg-config` does not find the `.pc` files for libcap.
+# We work around this by merging /usr/lib64/pkgconfig and
+# /usr/lib/pkgconfig.
+${target}-emerge -bk1vnj sys-libs/libcap
+if [ -d /usr/${target}/usr/lib/pkgconfig ] \
+        && [ ! -d /usr/${target}/usr/lib64/pkgconfig ]; then
+    mv /usr/${target}/usr/lib/pkgconfig /usr/${target}/usr/lib64
+    ln -snf ../lib64/pkgconfig /usr/${target}/usr/lib/pkgconfig
+fi
 
 if [ ! -d /usr/${target}/etc/portage/make.conf ]; then
     mv /usr/${target}/etc/portage/make.conf \
         /usr/${target}/etc/portage/make.conf.orig
+    sed -ri 's: ?-pam::' /usr/${target}/etc/portage/make.conf.orig
+    ls -l /usr/${target}/etc/portage
     mkdir /usr/${target}/etc/portage/make.conf
     mv /usr/${target}/etc/portage/make.conf.orig \
         /usr/${target}/etc/portage/make.conf/10-base.conf
@@ -31,8 +43,14 @@ if [ ! -d /etc/portage/make.conf ]; then
         /etc/portage/make.conf/10-base.conf
 fi
 
-# Set the Portage profile
+ln -snf /var/db/repos/gentoo/profiles/default/linux/${ARCH}/17.0 \
-ln -snf \
-    /var/db/repos/gentoo/profiles/${profile} \
     /usr/${target}/etc/portage/make.profile
 
+${target}-emerge -bk1nvj sys-libs/glibc
+
+${target}-emerge -bknvj sys-apps/util-linux
+
+# Migrate to the merged-usr layout
+mkdir -p /usr/${target}/bin
+emerge -bknv --quiet-build=y merge-usr
+merge-usr --root=/usr/${target}