git is not present in the debian build system

--- a/sidekiq.gemspec
+++ b/sidekiq.gemspec
@@ -10,7 +10,7 @@
   gem.license       = "LGPL-3.0"
 
   gem.executables   = ['sidekiq', 'sidekiqctl']
-  gem.files         = `git ls-files | grep -Ev '^(test|myapp|examples)'`.split("\n")
+  gem.files         = Dir.glob("**/*").select {|v| v !~ /^(test|myapp|examples|debian)/}
   gem.test_files    = []
   gem.name          = "sidekiq"
   gem.require_paths = ["lib"]