Fix cromo build under platform2.

This CL fixes two issues when building the cromo target under platform2:
1. Add the missing PLUGINDIR definition, which specifies the plugin
   directory.
2. Instead of statically linking against libcromo.a, explicitly link
   against individual objects in order to allow symbols, as specified in
   cromo.ver, to be exported to a cromo plugin.

BUG=chromium:313099
TEST=Tested the following for lumpy and daisy with Gobi3k modem:
1. `FEATURES=test emerge-$BOARD platform2`
2. Verify that cromo can load the gobi and madison plugin.

Change-Id: Ifc759c38dd8a01256cfa363c21e5c31814434dec
Reviewed-on: https://chromium-review.googlesource.com/175054
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
1 file changed