Added initial gemspec for zlib module.

[Feature #13186]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57512 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/zlib/zlib.gemspec

@@ -0,0 +1,17 @@
+Gem::Specification.new do |s|
+  s.name = "zlib"
+  s.version = '0.0.1'
+  s.date = '2017-02-03'
+  s.summary = "An interface for zlib."
+  s.description = "An interface for zlib."
+
+  s.require_path = %w{lib}
+  s.files = %w{depend extconf.rb zlib.c}
+  s.extensions = %w{extconf.rb}
+  s.required_ruby_version = ">= 2.5.0"
+
+  s.authors = ["UENO Katsuhiro"]
+  s.email = [nil]
+  s.homepage = "https://www.ruby-lang.org"
+  s.license = "BSD-2-Clause"
+end