Add platform/external/v8

BUG:18398366
Change-Id: I6c2577e307dc931e0660d0cf6500d339d39f4769

default.xml

@@ -269,6 +269,7 @@
   <project path="external/tinyxml2" name="platform/external/tinyxml2" groups="pdk" />
   <project path="external/toybox" name="platform/external/toybox" groups="pdk" />
   <project path="external/tremolo" name="platform/external/tremolo" groups="pdk" />
+  <project path="external/v8" name="platform/external/v8" groups="pdk" />
   <project path="external/valgrind" name="platform/external/valgrind" groups="pdk" />
   <project path="external/vixl" name="platform/external/vixl" groups="pdk" />
   <project path="external/vogar" name="platform/external/vogar" groups="pdk" />