Don't let pytest discover tests from test_cmake_build and test_embed

pytest raises an error if it recurses into these directories.
diff --git a/tests/pytest.ini b/tests/pytest.ini
index cd6da3a..1e44f0a 100644
--- a/tests/pytest.ini
+++ b/tests/pytest.ini
@@ -1,5 +1,6 @@
 [pytest]
 minversion = 3.0
+norecursedirs = test_cmake_build test_embed
 addopts =
     # show summary of skipped tests
     -rs