Remove pre-generated cython files.

[hzeller]

They easily get stale, and it is better to re-generate at compile time.

[hzeller]

CC @neuschaefer to review.

[neuschaefer]

Probably also a good idea:

diff --git a/shell.nix b/shell.nix
index 94d8a86..d19591e 100644
--- a/shell.nix
+++ b/shell.nix
@@ -11,5 +11,6 @@ pkgs.mkShell {
       ffmpeg
       pkg-config
       python3
+      python3Packages.cython
     ];
 }

[hzeller]

Probably also a good idea: (add stuff to shell.nix)

Thanks. Also had to add distutils-extra; it looks like the distutils stuff is deprecated and removed in 3.12, but I don't know enough about Python to fix that. Up for refinement :)