See http://code.google.com/p/google-web-toolkit/issues/detail?id=6015

Log error instead of throwing when a generated unit cannot be transferred to a
file, so that filenames exceeding file system limits don't make the whole build
fail).

Patch from tbroyer

http://gwt-code-reviews.appspot.com/1382801/


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10170 8db76d5a-ed1c-0410-87a9-c151d255dfc7