flake8/mypy: Ignore build folder

setup.cfg

@@ -30,12 +30,12 @@ known_third_party = defusedxml,passlib,pkg_resources,pytest,vobject
 # Only enable default tests (https://github.com/PyCQA/flake8/issues/790#issuecomment-812823398)
 select = E,F,W,C90,DOES-NOT-EXIST
 ignore = E121,E123,E126,E226,E24,E704,W503,W504,DOES-NOT-EXIST
-extend-exclude = ./build/
+extend-exclude = build
 
 [mypy]
 ignore_missing_imports = True
 show_error_codes = True
-exclude = ^build/
+exclude = (^|/)build($|/)
 
 [coverage:run]
 branch = True