tools-musl: fix when portage_confdir is missing.

tools-musl/run-ppc.sh

@@ -27,6 +27,11 @@ prepare_confs() {
         -e "s:FLAVOR:${flavor}:g" \
         -e "s:MYCATALYST:$(pwd):g" \
         >  stage${s}-${arch}-musl-${flavor}.conf
+
+    portage_confdir=$(grep portage_confdir stage${s}-${arch}-musl-${flavor}.conf \
+      | sed -e 's/^.*://')
+    [[ ! -e ${portage_confdir} ]] && sed -i -e '/^portage_confdir/d' \
+      stage${s}-${arch}-musl-${flavor}.conf
   done
 
   sed -i "/^chost/d" stage3-${arch}-musl-${flavor}.conf