Update gc from 7.2g to 7.6.0

packages/gc.rb

@@ -3,16 +3,20 @@ require 'package'
 class Gc < Package
   description 'A garbage collector for C and C++.'
   homepage 'http://www.hboehm.info/gc/'
-  version '7.2g'
-  source_url 'http://www.hboehm.info/gc/gc_source/gc-7.2g.tar.gz'
-  source_sha256 '584e29e2f1be4a389ca30f78dcd2c991031e7d1e1eb3d7ce2a0f975218337c2f'
+  version '7.6.0'
+  source_url 'http://www.hboehm.info/gc/gc_source/gc-7.6.0.tar.gz'
+  source_sha256 'a14a28b1129be90e55cd6f71127ffc5594e1091d5d54131528c24cd0c03b7d90'
+
+  depends_on 'libatomic_ops'
+  depends_on 'libtool'
 
   def self.build
-    system "./configure --prefix=/usr/local"
-    system "make"
+    system './configure'
+    system 'make'
   end
 
   def self.install
     system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+    system "libtool --finish /usr/local/lib"
   end
 end