Use forked portage-stable in manifest

BUG=b/162009712
TEST=init and sync

Change-Id: Ic5191f732a64e6842f986fac92f36e150711b818
diff --git a/external_full.xml b/external_full.xml
index aa69272..e02951b 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -24,9 +24,6 @@
   </notice>
 
   <!-- mirrored cros_sdk dependencies -->
-  <project path="src/third_party/portage-stable"
-           name="mirrors/cros/chromiumos/overlays/portage-stable"
-           revision="9804d0ae3abf8944109b823d6a588411bf32d3b2" />
   <project path="chromite"
            name="mirrors/cros/chromiumos/chromite"
            revision="c3a81f99020dd6ffd637f40562a9840b8dadf840" />
@@ -86,6 +83,8 @@
   <!-- COS sources -->
   <project path="src/overlays"
            name="cos/overlays/board-overlays" />
+  <project path="src/third_party/portage-stable"
+           name="third_party/overlays/portage-stable" />
   <project path="manifest" name="cos/manifest" >
       <copyfile src="LICENSE" dest="LICENSE" />
   </project>