ci: save pdb files for testing builds (#20407)

appveyor.yml

@@ -103,6 +103,11 @@ build_script:
       if ($env:GN_CONFIG -eq 'release') {
         python electron\script\zip-symbols.py
         appveyor PushArtifact out/Default/symbols.zip
+      } else {
+        # It's useful to have pdb files when debugging testing builds that are
+        # built on CI.
+        7z a pdb.zip out\Default\*.pdb
+        appveyor PushArtifact pdb.zip
       }
   - python electron/script/zip_manifests/check-zip-manifest.py out/Default/dist.zip electron/script/zip_manifests/dist_zip.win.%TARGET_ARCH%.manifest
 test_script: