Fix a error in a before(:suite) hook

https://github.com/ruby/actions/runs/703745101?check_suite_focus=true#step:16:27
```
An error occurred in a `before(:suite)` hook.
Failure/Error: contents = File.read(version_file)

Errno::ENOENT:
  No such file or directory @ rb_sysopen - /home/runner/work/actions/actions/snapshot-master/tmp/1/bundler-2.2.0.dev/lib/bundler/version.rb
```

spec/bundler/support/path.rb

@@ -235,6 +235,24 @@ module Spec
 
     def git_ls_files(glob)
       sys_exec("git ls-files -z -- #{glob}", :dir => source_root).split("\x0")
+    ensure
+      if err == "fatal: not a git repository (or any of the parent directories): .git"
+        @command_executions.pop # Remove failed "git ls-files"
+        Dir.chdir(source_root) do
+          files = []
+          Dir.glob(glob.shellsplit) do |path|
+            if File.directory?(path)
+              Dir.glob("#{path}/**/{*,.*}") do |sub_path|
+                next if File.directory?(sub_path)
+                files << sub_path
+              end
+            else
+              files << path
+            end
+          end
+          return files.uniq
+        end
+      end
     end
 
     def tracked_files_glob