rubyspec/core/io/popen_spec: avoid lingering "ruby -e sleep" process

The ruby_cmd helper blindly escapes code blocks passed to it,
causing "sleep" to be quoted in the command-line.  This quoting
results in IO.popen using a subshell (/bin/sh) to run the given
string command instead of invoking the Ruby executable directly.

Thus, IO.popen would only see the PID of the subshell via
IO#pid, and merely sending SIGKILL to the subshell would not
result in the child ("ruby -e sleep") being killed.

This problem with lingering ruby processes was easier to
reproduce on slow or heavily-loaded systems using low-scheduling
priority (e.g. "chrt -i 0 make test-rubyspec")

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58863 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/rubyspec/core/io/popen_spec.rb

@@ -74,8 +74,12 @@ describe "IO.popen" do
   end
 
   it "does not throw an exception if child exited and has been waited for" do
-    @io = IO.popen(ruby_cmd('sleep'))
-    Process.kill "KILL", @io.pid
+    # Avoid the /bin/sh subshell using :options and :args to sleep.
+    # We don't want to kill only the subshell and leave "ruby -e sleep"
+    # running indefinitely
+    @io = IO.popen(ruby_cmd(nil, :options => '-e', :args => 'sleep'))
+    pid = @io.pid
+    Process.kill "KILL", pid
     @io.close
     platform_is_not :windows do
       $?.signaled?.should == true