diff --git a/build_library/catalyst_toolchains.sh b/build_library/catalyst_toolchains.sh
index 1e0ea642f5..c09ebbfd9a 100644
--- a/build_library/catalyst_toolchains.sh
+++ b/build_library/catalyst_toolchains.sh
@@ -11,83 +11,18 @@ source /tmp/toolchain_util.sh
 # build deps in crossdev's sysroot use ${PKGDIR}/cross/${CHOST} (no upload)
 # native toolchains use ${PKGDIR}/target/${BOARD} (uploaded to board location)
 
-get_dependency_list() {
-    local ROOT="$1"
-    local IFS=$'| \t\n'
-    shift
-
-    PORTAGE_CONFIGROOT="$ROOT" SYSROOT="$ROOT" \
-        ROOT="$ROOT" emerge ${clst_myemergeopts} \
-        --pretend --with-bdeps=y --onlydeps --quiet \
-        "$@" | sed -e 's/.*\] \([^ :]*\).*/=\1/' |
-        egrep -v "(=$(echo "$*")-[0-9])"
-}
-
-configure_portage() {
-    local pkg_path="$1"
-    local profile="$2"
-
-    mkdir -p "${ROOT}/etc/portage"
-    echo "eselect will report '!!! Warning: Strange path.' but that's OK"
-    eselect profile set --force "$profile"
-
-    cat >"${ROOT}/etc/portage/make.conf" <<EOF
-CHOST=${CHOST}
-CBUILD=$(portageq envvar CBUILD)
-HOSTCC=\${CBUILD}-gcc
-ROOT="${ROOT}"
-SYSROOT="${SYSROOT}"
-PKG_CONFIG_PATH="\${SYSROOT}/usr/lib/pkgconfig/"
-PORTDIR="$(portageq envvar PORTDIR)"
-DISTDIR="\${PORTDIR}/distfiles"
-PKGDIR="\${PORTDIR}/packages/${pkg_path}"
-PORTDIR_OVERLAY="$(portageq envvar PORTDIR_OVERLAY)"
-EOF
-}
-
-build_cross_toolchain() {
-    local cross_chost="$1"
-    local cross_pkgs=( $(get_cross_pkgs $cross_chost) )
-    local PORTDIR="$(portageq envvar PORTDIR)"
-    local PKGDIR="${PORTDIR}/packages/crossdev"
-
-    PKGDIR="${PKGDIR}" crossdev \
-        --ov-output "/tmp/crossdev" --stable \
-        --portage "${clst_myemergeopts}" \
-        --init-target --target "${cross_chost}"
-
-    # If PKGCACHE is enabled check to see if binary packages are available.
-    # If so then don't perform a full bootstrap and just call emerge instead.
-    if [[ -n "${clst_PKGCACHE}" ]] && \
-        PKGDIR="${PKGDIR}" emerge ${clst_myemergeopts} \
-            --usepkgonly --binpkg-respect-use=y \
-            --pretend "${cross_pkgs[@]}" &>/dev/null
-    then
-        PKGDIR="${PKGDIR}" run_merge -u "${cross_pkgs[@]}"
-    else
-        PKGDIR="${PKGDIR}" crossdev \
-            --ov-output "/tmp/crossdev" --stable \
-            --env PKGDIR="${PORTDIR}/packages/crossdev" \
-            --portage "${clst_myemergeopts}" \
-            --stage4 --target "${cross_chost}"
-    fi
-
-    # Setup ccache for our shiny new toolchain
-    ccache-config --install-links "${cross_chost}"
-}
-
-configure_cross_root() {
+build_cross_libs() {
     local cross_chost="$1"
     local ROOT="/usr/${cross_chost}"
 
     CHOST="${cross_chost}" ROOT="$ROOT" SYSROOT="$ROOT" \
-        configure_portage "cross/${cross_chost}" \
-        "${CROSS_PROFILE[${cross_chost}]}"
+        _configure_sysroot "${CROSS_PROFILE[${cross_chost}]}"
 
     # In order to get a dependency list we must calculate it before
     # updating package.provided. Otherwise portage will no-op.
-    get_dependency_list "$ROOT" "${TOOLCHAIN_PKGS[@]}" \
-        > "$ROOT/etc/portage/cross-${cross_chost}-depends"
+    ROOT="$ROOT" _get_dependency_list \
+        ${clst_myemergeopts} "${TOOLCHAIN_PKGS[@]}" > \
+        "$ROOT/etc/portage/cross-${cross_chost}-depends"
 
     # Add toolchain to packages.provided since they are on the host system
     mkdir -p "$ROOT/etc/portage/profile/package.provided"
@@ -97,11 +32,6 @@ configure_cross_root() {
         cross_pkg_version=$(portageq match / "${cross_pkg}")
         echo "${native_pkg%/*}/${cross_pkg_version#*/}"
     done > "$ROOT/etc/portage/profile/package.provided/cross-${cross_chost}"
-}
-
-build_cross_libs() {
-    local cross_chost="$1"
-    local ROOT="/usr/${cross_chost}"
     local cross_deps=$(<"$ROOT/etc/portage/cross-${cross_chost}-depends")
 
     # --root is required because run_merge overrides ROOT=
@@ -111,10 +41,12 @@ build_cross_libs() {
 configure_target_root() {
     local board="$1"
     local cross_chost=$(get_board_chost "$1")
+    local profile=$(get_board_profile "${board}")
 
-    CHOST="${cross_chost}" ROOT="/build/${board}" \
-        SYSROOT="/usr/${cross_chost}" configure_portage \
-        "target/${board}" "$(get_board_profile "${board}")"
+    CHOST="${cross_chost}" \
+        ROOT="/build/${board}" \
+        SYSROOT="/usr/${cross_chost}" \
+        _configure_sysroot "${profile}"
 }
 
 build_target_toolchain() {
@@ -126,15 +58,21 @@ build_target_toolchain() {
         run_merge -u --root="$ROOT" "${TOOLCHAIN_PKGS[@]}"
 }
 
+mkdir -p "/tmp/crossdev"
+export PORTDIR_OVERLAY="/tmp/crossdev $(portageq envvar PORTDIR_OVERLAY)"
+
 for cross_chost in $(get_chost_list); do
     echo "Building cross toolchain for ${cross_chost}"
-    build_cross_toolchain "${cross_chost}"
-    configure_cross_root "${cross_chost}"
-    build_cross_libs "${cross_chost}"
+    PKGDIR="$(portageq envvar PKGDIR)/crossdev" \
+        install_cross_toolchain "${cross_chost}" ${clst_myemergeopts}
+
+    sysroot_pkgdir="$(portageq envvar PKGDIR)/cross/${cross_chost}"
+    PKGDIR="${sysroot_pkgdir}" build_cross_libs "${cross_chost}"
 done
 
 for board in $(get_board_list); do
     echo "Building native toolchain for ${board}"
-    configure_target_root "${board}"
-    build_target_toolchain "${board}"
+    target_pkgdir="$(portageq envvar PKGDIR)/target/${board}"
+    PKGDIR="${target_pkgdir}" configure_target_root "${board}"
+    PKGDIR="${target_pkgdir}" build_target_toolchain "${board}"
 done
diff --git a/build_library/toolchain_util.sh b/build_library/toolchain_util.sh
index f51e8d16ac..231f9b3ea8 100644
--- a/build_library/toolchain_util.sh
+++ b/build_library/toolchain_util.sh
@@ -71,3 +71,87 @@ get_cross_pkgs() {
         done
     done
 }
+
+### Toolchain building utilities ###
+
+# Ugly hack to get a dependency list of a set of packages.
+# This is required to figure out what to install in the crossdev sysroot.
+# Usage: ROOT=/foo/bar _get_dependency_list pkgs... [--portage-opts...]
+_get_dependency_list() {
+    local pkgs=( ${*/#-*/} )
+    local IFS=$'| \t\n'
+
+    PORTAGE_CONFIGROOT="$ROOT" emerge "$@" --pretend \
+        --emptytree --root-deps=rdeps --onlydeps --quiet | \
+        sed -e 's/.*\] \([^ :]*\).*/=\1/' |
+        egrep -v "(=$(echo "${pkgs[*]}")-[0-9])"
+}
+
+# Configure a new ROOT
+# Values are copied from the environment or the current host configuration.
+# Usage: ROOT=/foo/bar SYSROOT=/foo/bar configure_portage coreos:some/profile
+_configure_sysroot() {
+    local profile="$1"
+
+    mkdir -p "${ROOT}/etc/portage"
+    echo "eselect will report '!!! Warning: Strange path.' but that's OK"
+    eselect profile set --force "$profile"
+
+    cat >"${ROOT}/etc/portage/make.conf" <<EOF
+$(portageq envvar -v CHOST CBUILD ROOT SYSROOT \
+    PORTDIR PORTDIR_OVERLAY DISTDIR PKGDIR)
+HOSTCC=\${CBUILD}-gcc
+PKG_CONFIG_PATH="\${SYSROOT}/usr/lib/pkgconfig/"
+EOF
+}
+
+# Dump crossdev information to determine if configs must be reganerated
+_crossdev_info() {
+    local cross_chost="$1"; shift
+    echo -n "# "; crossdev --version
+    echo "# $@"
+    crossdev --show-target-cfg "${cross_chost}"
+}
+
+# Build/install a toolchain w/ crossdev.
+# Usage: build_cross_toolchain chost [--portage-opts....]
+install_cross_toolchain() {
+    local cross_chost="$1"; shift
+    local cross_pkgs=( $(get_cross_pkgs $cross_chost) )
+    local cross_cfg="/usr/${cross_chost}/etc/portage/${cross_chost}-crossdev"
+    local cross_cfg_data=$(_crossdev_info "${cross_chost}" stable)
+
+    # may be called from either catalyst (root) or upgrade_chroot (user)
+    local sudo=
+    if [[ $(id -u) -ne 0 ]]; then
+        sudo="sudo -E"
+    fi
+
+    # Only call crossdev to regenerate configs if something has changed
+    if ! cmp --quiet - "${cross_cfg}" <<<"${cross_cfg_data}"
+    then
+        $sudo crossdev --stable --portage "$*" \
+            --init-target --target "${cross_chost}"
+        sudo_clobber "${cross_cfg}" <<<"${cross_cfg_data}"
+    fi
+
+    # If binary packages are enabled try to just emerge them instead of
+    # doing a full bootstrap which speeds things up greatly. :)
+    if [[ "$*" == *--usepkg* ]] && \
+        emerge "$@" --usepkgonly --binpkg-respect-use=y \
+            --pretend "${cross_pkgs[@]}" &>/dev/null
+    then
+        $sudo emerge "$@" --binpkg-respect-use=y -u "${cross_pkgs[@]}"
+    else
+        $sudo crossdev --stable --portage "$*" \
+            --stage4 --target "${cross_chost}"
+    fi
+
+    # Setup wrappers for our shiny new toolchain
+    if [[ ! -e "/usr/lib/ccache/bin/${cross_chost}-gcc" ]]; then
+        $sudo ccache-config --install-links "${cross_chost}"
+    fi
+    if [[ ! -e "/usr/lib/sysroot-wrappers/bin/${cross_chost}-gcc" ]]; then
+        $sudo sysroot-config --install-links "${cross_chost}"
+    fi
+}