fix(dev-infra): browser archive rule should handle `.dmg` files (#42992)

We recently reworked our browser archive extraction to happen
at analysis time for better caching. This resulted in us breaking
the extraction of macOS dmg files so that Firefox is currently
not usable for local testing on macOS. We implement a similar special
logic for `.dmg` files to what has been done within the Bazel
webtesting rules.

PR Close #42992

dev-infra/bazel/browsers/browser_archive_repo.bzl

@@ -1,10 +1,26 @@
 """Implementation of the `browser_archive` rule."""
 
 def _browser_archive_impl(ctx):
-    ctx.report_progress("Downloading browser archive from: %s" % ctx.attr.url)
+    url = ctx.attr.url
+    sha256 = ctx.attr.sha256
+
+    # If the URL resolves to a `.dmg` file, then we need to convert the file
+    # to a zip so that we can extract the actual binaries. We use the `convert_dmg`
+    # script provided by the webtesting Bazel rules.
+    if url.endswith(".dmg"):
+        download_file_name = "_download_file_%s.dmg" % ctx.attr.name
+        result_zip_name = "_converted_file_%s.zip" % ctx.attr.name
+
+        ctx.download(url, download_file_name, sha256)
+        ctx.execute([ctx.path(Label("@io_bazel_rules_webtesting//web/internal:convert_dmg.sh")), download_file_name, result_zip_name])
+        ctx.extract(result_zip_name)
+
+        ctx.delete(result_zip_name)
+        ctx.delete(download_file_name)
+    else:
         ctx.download_and_extract(
-        url = ctx.attr.url,
-        sha256 = ctx.attr.sha256,
+            url = url,
+            sha256 = sha256,
         )
 
     # The browser archive has been downloaded and extracted. We now generate a repository