Specify the full path to atree for the windows.atree

Somehow the build server doesn't automatically find atree.
In a future CL this should be amended to pass the proper
OUT_HOST_EXECUTABLE, being careful that it points to the
host/linux dir, not the current Windows one.

Change-Id: Ibb78a517c33d46454828a5932408108dadbee497
1 file changed