libapparmor: fix build if doCheck = false (e.g. on cross)

This is a HACK. The correct fix is #401980,
but causes rebuilds and therefore is unsuitable for staging-next.

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

@@ -58,6 +58,16 @@ stdenv.mkDerivation (finalAttrs: {
     ]
     ++ lib.optionals withPython [
       python3Packages.setuptools
+    ]
+    ++ lib.optionals (!finalAttrs.finalPackage.doCheck) [
+      # TODO FIXME This is a super ugly HACK.
+      # perl is required for podchecker.
+      # It is a native build input on native platform because checks are enabled there.
+      # Checks can't be enabled on cross, but moving perl to
+      # nativeCheckInputs causes rebuilds on native compile.
+      # Thus, hacks!
+      # This should just be made unconditional and removed from nativeCheckInputs.
+      perl
     ];
 
   nativeCheckInputs = [