* tool/fake.rb: Fix cross build when srcdir is an absolute path.
* Makefile.in: PREP dependency is needed when cross build too, not
"-r$(arch)-fake" to be used before created. [Fix GH-1125]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52898 b2dd03c8-39d4-4d8f-98ff-823fe69b080e