Get pybind11 test suite to compile on the Intel compiler (more or less..)

- ICPC can't handle the NCVirt trampoline which returns a non-copyable
  type, which is likely due to a constexpr/SFINAE issue. This disables
  the test on that compiler so that at least the rest can be tested.

tests/test_virtual_functions.py

@@ -1,4 +1,5 @@
 import pytest
+import pybind11_tests
 from pybind11_tests import ConstructorStats
 
 
@@ -150,7 +151,7 @@ def test_inheriting_repeat():
     assert obj.unlucky_number() == 1234
     assert obj.lucky_number() == -4.25
 
-
+@pytest.mark.skipif(not hasattr(pybind11_tests, 'NCVirt'))
 def test_move_support():
     from pybind11_tests import NCVirt, NonCopyable, Movable