Update get_pybind11_include

Author: isuruf

pybind11/__init__.py

@@ -4,4 +4,9 @@
 def get_include(user=False):
     import os
     d = os.path.dirname(__file__)
-    return os.path.join(os.path.dirname(d), "include")
+    if os.path.exists(os.path.join(d, "include")):
+        # Package is installed
+        return os.path.join(d, "include")
+    else:
+        # Package is from a source directory
+        return os.path.join(os.path.dirname(d), "include")