gdu: fix test skipping

This wasn't working as intended, as the skip flag was added
twice, which caused the second occurrence to overwrite the first,
and the build to fail on aarch64-linux, see
https://hydra.nixos.org/build/308978158/nixlog/1

Signed-off-by: Paul Meyer <katexochen0@gmail.com>

pkgs/by-name/gd/gdu/package.nix

@@ -42,11 +42,14 @@ buildGoModule (finalAttrs: {
 
   doCheck = !stdenv.hostPlatform.isDarwin;
 
-  checkFlags = [
-    # https://github.com/dundee/gdu/issues/371
-    "-skip=TestStoredAnalyzer"
-    "-skip=TestAnalyzePathWithIgnoring"
-  ];
+  checkFlags =
+    let
+      skippedTests = [
+        "TestStoredAnalyzer" # https://github.com/dundee/gdu/issues/371
+        "TestAnalyzePathWithIgnoring"
+      ];
+    in
+    [ "-skip=^${builtins.concatStringsSep "$|^" skippedTests}$" ];
 
   doInstallCheck = true;