Move -soyc flag up to Precompile so that it works with both compiler entry
points.
Patch by: jgw
Review by: scottb,spoon
Review: http://gwt-code-reviews.appspot.com/22802


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@5238 8db76d5a-ed1c-0410-87a9-c151d255dfc7