Auto merge of #6336 - bundler:segiddins/updater-use-more-filesystem-a…

…ccess, r=colby-swandale

[CompactIndexClient::Updater] Use filesystem_access when copying files

### What was the end-user problem that led to this PR?

The problem was users could see the error template when they do not have write permissions to their temporary directory.

Closes #6289

### What was your diagnosis of the problem?

My diagnosis was we need to use `SharedHelpers.filesystem_access` when writing files.

### What is your fix for the problem, implemented in this PR?

My fix wraps usage of `cp`

(cherry picked from commit b7b847f)

lib/bundler/compact_index_client/updater.rb

@@ -33,7 +33,9 @@ def update(local_path, remote_path, retrying = nil)
 
           # first try to fetch any new bytes on the existing file
           if retrying.nil? && local_path.file?
-            FileUtils.cp local_path, local_temp_path
+            SharedHelpers.filesystem_access(local_temp_path) do
+              FileUtils.cp local_path, local_temp_path
+            end
             headers["If-None-Match"] = etag_for(local_temp_path)
             headers["Range"] =
               if local_temp_path.size.nonzero?