File.mtime causes an exception if the file does not exist under win32 so avoid this scenario
File.mtime causes an exception if the file does not exist under win32 so avoid this scenario

git-svn-id: d8f3215415546ce936cf3b822120ca56e5ebeaa0@1400530 13f79535-47bb-0310-9956-ffa450edef68

liamchristopher/buildr,mariusk/buildr-kawa,jpcaruana/buildr,mariusk/buildr-kawa,jpcaruana/buildr,jpcaruana/buildr,stewi2/buildr,stewi2/buildr,stewi2/buildr,liamchristopher/buildr,stewi2/buildr,mariusk/buildr-kawa,liamchristopher/buildr,apache/buildr,apache/buildr,apache/buildr,apache/buildr,liamchristopher/buildr,jpcaruana/buildr