Fixed Gemspec for compiling extensions

allocations.gemspec

@@ -9,6 +9,7 @@ Gem::Specification.new do |gem|
   gem.homepage    = 'https://gitlab.com/gitlab/allocations'
   gem.description = gem.summary
   gem.license     = 'MIT'
+  gem.extensions  = ['ext/liballocations/extconf.rb']
   gem.files = Dir.glob([
     'lib/**/*.rb',