Debian package build environment is not a git repo

--- a/shoulda-context.gemspec
+++ b/shoulda-context.gemspec
@@ -15,9 +15,11 @@
   s.description = "Context framework extracted from Shoulda"
   s.license     = "MIT"
 
-  s.files            = `git ls-files`.split("\n")
-  s.test_files       = `git ls-files -- {test,spec,features}/*`.split("\n")
-  s.executables      = `git ls-files -- exe/*`.split("\n").map { |f| File.basename(f) }
+  all_files          = Dir.glob("**/*").select {|v| v !~ /^debian/}
+  test_files         = all_files.select {|v| v =~ /^(test|spec|features)/}
+  s.files            = all_files - test_files
+  s.test_files       = test_files
+  s.executables      = all_files.select {|v| v =~ /^exe\//}.map { |f| File.basename(f) }
   s.bindir           = "exe"
   s.require_paths    = ["lib"]
 end