Fix file metadata when package is built outside of a git repository
--- a/chromedriver-helper.gemspec
+++ b/chromedriver-helper.gemspec
@@ -16,13 +16,10 @@ Gem::Specification.new do |s|
   s.description = "Easy installation and use of chromedriver, the Chromium project's selenium webdriver adapter."
   s.licenses    = ["MIT"]
 
-  begin
-    s.files         = `git ls-files`.split("\n")
-    s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
-    s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
-  rescue Exception => e
-    warn "WARNING: could not set spec.files: #{e.class}: #{e}"
-  end
+  s.files         = Dir['**/*'] - Dir['debian/**/*']
+  s.test_files    = Dir['{test,spec,features}/**/*']
+  s.executables   = Dir['bin/*'].map{ |f| File.basename(f) }
+
   s.require_paths = ["lib"]
 
   s.add_development_dependency "rspec",     "~> 3.0"