libgit2: universal option

Adds an universal option to libgit2.

Closes Homebrew/homebrew#35154.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/libgit2.rb

@@ -1,7 +1,7 @@
 require "formula"
 
 class Libgit2 < Formula
-  homepage "http://libgit2.github.com/"
+  homepage "https://libgit2.github.com/"
   url "https://github.com/libgit2/libgit2/archive/v0.21.3.tar.gz"
   sha1 "d116cb15f76edf2283c85da40389e4fecc8d5aeb"
 
@@ -14,16 +14,24 @@ class Libgit2 < Formula
     sha1 "059ee25e0a3d46ad685b3d55394ae1c8a007da70" => :mountain_lion
   end
 
+  option :universal
+
   depends_on "cmake" => :build
   depends_on "libssh2" => :optional
   depends_on "openssl"
 
   def install
+    args = std_cmake_args
+    args << "-DBUILD_TESTS=NO"
+
+    if build.universal?
+      ENV.universal_binary
+      args << "-DCMAKE_OSX_ARCHITECTURES=#{Hardware::CPU.universal_archs.as_cmake_arch_flags}"
+    end
+
     mkdir "build" do
-      system "cmake", "..",
-                      "-DBUILD_TESTS=NO",
-                      *std_cmake_args
-      system "make install"
+      system "cmake", "..", *args
+      system "make", "install"
     end
   end
 end