Add external/trusty

Bug: 119111590
Change-Id: I7e0f9bb37741f722b04c70e4df5c516b1c6067d7
diff --git a/default.xml b/default.xml
index e7762eb..ee342d6 100644
--- a/default.xml
+++ b/default.xml
@@ -13,6 +13,7 @@
     <copyfile src="makefile" dest="makefile" />
   </project>
   <project path="external/headers" name="trusty/external/headers" groups="trusty" />
+  <project path="external/trusty" name="trusty/external/trusty" groups="trusty" />
   <project path="trusty/user/base" name="trusty/lib" groups="trusty" />
   <project path="trusty/kernel" name="trusty/lk/trusty" groups="trusty" />
   <!-- END trusty core projects -->