not only when !w but also when w == WAITPID_LOCK_ONLY.
See also: f7c0cc3692 and a226434206.
We thought this change was an oversight in the latter commit.
Without this change, the test fails like:
$ make test-all TESTS="../test/ruby/test_process.rb -n test_exec_failure_leaves_no_child" RUN_OPTS="--jit"
...
1) Failure:
TestProcess#test_exec_failure_leaves_no_child [/home/k0kubun/src/github.com/ruby/ruby/test/ruby/test_process.rb:2493]:
Expected [[26799, #<Process::Status: pid 26799 exit 127>]] to be empty.
Co-Authored-By: Yusuke Endoh <mame@ruby-lang.org>