Use pkg-config to find system leveldb

Rakefile

@@ -10,13 +10,13 @@ spec = Gem::Specification.new do |s|
  s.authors = ["William Morgan"]
  s.summary = "a Ruby binding to LevelDB"
  s.homepage = "http://github.com/wmorgan/leveldb-ruby"
- s.files = %w(README LICENSE ext/leveldb/extconf.rb ext/leveldb/platform.rb lib/leveldb.rb ext/leveldb/leveldb.cc leveldb/Makefile leveldb/build_detect_platform)
- Find.find("leveldb") { |x| s.files += [x] if x =~ /\.(cc|h)$/}
+ s.files = %w(README LICENSE ext/leveldb/extconf.rb ext/leveldb/platform.rb lib/leveldb.rb ext/leveldb/leveldb.cc)
  s.extensions = %w(ext/leveldb/extconf.rb)
  s.executables = []
  s.extra_rdoc_files = %w(README ext/leveldb/leveldb.cc)
  s.rdoc_options = %w(-c utf8 --main README --title LevelDB)
  s.description = "LevelDB-Ruby is a Ruby binding to LevelDB."
+ s.licenses = ["BSD-3-Clause"]
 end
 
 task :rdoc do |t|

ext/leveldb/extconf.rb

@@ -2,13 +2,9 @@
 require 'fileutils'
 require "./platform.rb"
 
-Dir.chdir "../../leveldb"
-system "OPT=\"-O2 -DNDEBUG -fPIC\" make libleveldb.a" or abort
-Dir.chdir "../ext/leveldb"
-
 set_platform_specific_variables!
 
-$CFLAGS << " -I../../leveldb/include"
-$LIBS << " -L../../leveldb -lleveldb"
+$INCFLAGS << ' ' << `pkg-config --cflags-only-I leveldb`.strip << ' '
+$LIBS << ' ' << `pkg-config --libs leveldb`.strip << ' '
 
 create_makefile "leveldb/leveldb"