Checking clang include dir before adding it as 'isystem' parameter. Fixes #16

Author: Andreas Kunze

pybind11_mkdoc/mkdoc_lib.py

@@ -313,7 +313,8 @@ def folder_version(d):
                     glob(os.path.join(llvm_dir, 'lib', 'clang', '*')
                 ), default=None, key=folder_version)
 
-            parameters.extend(['-isystem', clang_include_dir])
+            if clang_include_dir is not None:
+                parameters.extend(['-isystem', clang_include_dir])
 
         # Add additional C++ include directories
         cpp_dirs = []