Non-parallel "make test-spec" caused
spec/ruby/core/process/wait2_spec.rb failures because mspec
uses "exec" in single-process mode, so there's no chance
the post-exec state could know about the MJIT child process
from its pre-exec state.
[ruby-core:87846] [Bug #14867]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63877 b2dd03c8-39d4-4d8f-98ff-823fe69b080e