Wait until excpetion handling is ready.

Because RubyCI on Solaris 10 failed as follows:

    1) Failure:
  TestProcess#test_execopts_redirect_open_fifo_interrupt_raise [/export/home/rubyci/unstable10s/tmp/build/20161130T201909Z/ruby/test/ruby/test_process.rb:646]:
  <"ok\n"> expected but was
  <"">.

The argument of sleep (0.5) can be smaller, but I'm not sure.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56954 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_process.rb

@@ -636,11 +636,14 @@ class TestProcess < Test::Unit::TestCase
         class E < StandardError; end
         trap(:USR1) { raise E }
         begin
+          puts "start"
+          STDOUT.flush
           system("cat", :in => "fifo")
         rescue E
           puts "ok"
         end
       EOS
+        assert_equal("start\n", io.gets)
         sleep 0.5
         Process.kill(:USR1, io.pid)
         assert_equal("ok\n", io.read)