Merge pull request #6545 from ThomasWaldmann/add-pyproject.toml-1.2

add pyproject.toml, fix sys.path, fixes #6466

pyproject.toml

@@ -0,0 +1,3 @@
+[build-system]
+requires = ["setuptools", "pkgconfig", "Cython"]
+build-backend = "setuptools.build_meta"

setup.py

@@ -19,6 +19,7 @@ try:
 except ImportError:
     cythonize = None
 
+sys.path += [os.path.dirname(__file__)]
 import setup_checksums
 import setup_compress
 import setup_crypto