dufs: fix build by adding cacert to preCheck (#526701)

pkgs/by-name/du/dufs/package.nix

@@ -4,6 +4,7 @@
   fetchFromGitHub,
   installShellFiles,
   stdenv,
+  cacert,
 }:
 
 rustPlatform.buildRustPackage (finalAttrs: {
@@ -23,6 +24,10 @@ rustPlatform.buildRustPackage (finalAttrs: {
 
   __darwinAllowLocalNetworking = true;
 
+  preCheck = ''
+    export SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt
+  '';
+
   checkFlags = [
     # tests depend on network interface, may fail with virtual IPs.
     "--skip=validate_printed_urls"