display stderr output even if core dump files

On btest, stderr messages are not displayed if core files are
generated. There is no reason to skip it, so this patch display
stderr and check core files.

bootstraptest/runner.rb

@@ -261,6 +261,14 @@ rescue Exception => err
   $stderr.print 'E'
   $stderr.puts if @verbose
   error err.message, message
+ensure
+  begin
+    check_coredump
+  rescue CoreDumpError => err
+    $stderr.print 'E'
+    $stderr.puts if @verbose
+    error err.message, message
+  end
 end
 
 def show_limit(testsrc, opt = '', **argh)
@@ -275,7 +283,6 @@ end
 def assert_check(testsrc, message = '', opt = '', **argh)
   show_progress(message) {
     result = get_result_string(testsrc, opt, **argh)
-    check_coredump
     yield(result)
   }
 end
@@ -453,7 +460,6 @@ def get_result_string(src, opt = '', **argh)
       `#{@ruby} -W0 #{opt} #{filename}`
     ensure
       raise Interrupt if $? and $?.signaled? && $?.termsig == Signal.list["INT"]
-      raise CoreDumpError, "core dumped" if $? and $?.coredump?
     end
   else
     eval(src).to_s