Create gtk3.rb

GTK+3 is available now.

packages/gtk3.rb

+require 'package'
+
+class Gtk3 < Package
+  description 'Gtk3 is a cross-platform widget toolkit for creating graphical user interfaces.'
+  homepage 'https://developer.gnome.org/gtk3/3.0/'
+  version '3.26'
+  source_url 'http://ftp.gnome.org/pub/gnome/sources/gtk+/3.22/gtk+-3.22.26.tar.xz'
+  source_sha256 '61eef0d320e541976e2dfe445729f12b5ade53050ee9de6184235cb60cd4b967'
+
+  depends_on 'glib'
+  depends_on 'gobject_introspection'
+  depends_on 'gdk_pixbuf'
+  depends_on 'cairo'
+  depends_on 'pango'
+  depends_on 'libepoxy'
+  depends_on 'graphene'
+  depends_on 'atk'
+  depends_on 'libxkbcommon'
+  depends_on 'meson'
+  depends_on 'ninja'
+  depends_on 'python3'
+  depends_on 'libx11'
+  depends_on 'at_spi2_atk'
+
+  def self.build
+    system "./configure --prefix=#{CREW_PREFIX} --libdir=#{CREW_LIB_PREFIX}"
+    system "make"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+
+end