For flake8 skip build folder

Author: vitodb

.flake8

@@ -2,6 +2,8 @@
 # SPDX-License-Identifier: Apache-2.0
 [flake8]
   max-line-length = 120
+  # Do not test build folder
+  extend-exclude = ./build
   # Errors and warnings to ignore
   extend-ignore =
      # line too long (90 > 79 characters)