Formula for the Shapefile C library

This doesn't have a configure script, and the Makefile is basic. Installation
steps are based on the macports portfile.

Signed-off-by: Max Howell <max@methylblue.com>

Replaced most system calls with Ruby equivalents.

Formula/shapefile.rb

@@ -0,0 +1,29 @@
+require 'formula'
+
+class Shapefile <Formula
+  url 'http://download.osgeo.org/shapelib/shapelib-1.2.10.tar.gz'
+  homepage 'http://shapelib.maptools.org/'
+  md5 '4d96bd926167193d27bf14d56e2d484e'
+
+  def install
+    dylib = lib+"libshp.#{version}.dylib"
+
+    inreplace 'Makefile', /CFLAGS\s+=\s+-g/, "CFLAGS = #{ENV['CFLAGS']}"
+
+    system "make all"
+    system "make shptree.o"
+
+    lib.mkpath
+    system ENV.cc, *%W(-dynamiclib -all_load
+                       -install_name #{dylib}
+                       -compatibility_version #{version}
+                       -o #{dylib}
+                       shpopen.o shptree.o dbfopen.o)
+
+    include.install 'shapefil.h'
+
+    Dir.chdir lib
+    FileUtils.ln_s "libshp.#{version}.dylib", "libshp.#{version.split('.').first}.dylib"
+    FileUtils.ln_s "libshp.#{version}.dylib", "libshp.dylib"
+  end
+end