Update cygwin/GNUmakefile.in
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55467 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Update cygwin/GNUmakefile.in
include defs/gmake.mk to serialize test targets.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55467 b2dd03c8-39d4-4d8f-98ff-823fe69b080e