Skip test which fails with ALLOW_SUBPROCESSES=false

Author: eregon

test/mri/tests/mkmf/test_install.rb

@@ -3,6 +3,8 @@
 
 class TestMkmfInstall < TestMkmf
   def test_install_dirs
+    skip 'does not work with !ALLOW_SUBPROCESSES' unless Test::Unit::CoreAssertions::ALLOW_SUBPROCESSES
+
     Dir.mktmpdir do |dir|
       File.write(dir+"/extconf.rb", "require 'mkmf'; create_makefile('test')")
       all_assertions do |a|