libcaca: fix build on Darwin

libcaca tries to access a private API that is no longer available. It
worked before the SDK changes because no Darwin frameworks were
available in the build environment, but there is now always an SDK
available, causing it to try to build Cocoa code that no longer works.

pkgs/by-name/li/libcaca/package.nix

@@ -39,6 +39,10 @@ stdenv.mkDerivation rec {
 
   configureFlags = [
     (if x11Support then "--enable-x11" else "--disable-x11")
+  ] ++ lib.optionals stdenv.hostPlatform.isDarwin [
+    # Suppresses a build failure building Cocoa support due to accessing private ivar `_running`,
+    # which no longer available.
+    (lib.enableFeature false "cocoa")
   ];
 
   env.NIX_CFLAGS_COMPILE = lib.optionalString (!x11Support) "-DX_DISPLAY_MISSING";