git is not present in the debian build system

--- a/sidekiq.gemspec
+++ b/sidekiq.gemspec
@@ -9,7 +9,7 @@
   gem.license = "LGPL-3.0"
 
   gem.executables = ["sidekiq", "sidekiqmon"]
-  gem.files = `git ls-files | grep -Ev '^(test|myapp|examples)'`.split("\n")
+  gem.files         = Dir.glob("**/*").select {|v| v !~ /^(test|myapp|examples|debian)/}
   gem.name = "sidekiq"
   gem.version = Sidekiq::VERSION
   gem.required_ruby_version = ">= 2.5.0"