Find dlltool from RbConfig and update rake-compiler for cross-compilation

Author: sodabrew

ext/mysql2/extconf.rb

@@ -104,19 +104,24 @@ def asplode lib
   libfile = File.expand_path(File.join(rpath_dir, 'libmysql.lib'))
   file 'libmysql.a' => [deffile, libfile] do |t|
     when_writing 'building libmysql.a' do
-      sh 'dlltool', '--kill-at',
+      # Ruby kindly shows us where dllwrap is, but that tool does more than we want.
+      # Maybe in the future Ruby could provide RbConfig::CONFIG['DLLTOOL'] directly.
+      dlltool = RbConfig::CONFIG['DLLWRAP'].gsub('dllwrap', 'dlltool')
+      sh dlltool, '--kill-at',
          '--dllname', 'libmysql.dll',
          '--output-lib', 'libmysql.a',
          '--input-def', deffile, libfile
     end
   end
 
   Rake::Task['libmysql.a'].invoke
-
-  # Make sure the generated interface library works
   $LOCAL_LIBS << ' ' << 'libmysql.a'
-  abort "-----\nCannot find libmysql.a\n----" unless have_library('libmysql')
-  abort "-----\nCannot link to libmysql.a (my_init)\n----" unless have_func('my_init')
+
+  # Make sure the generated interface library works (if cross-compiling, trust without verifying)
+  unless RbConfig::CONFIG['host_os'] =~ /mswin|mingw/
+    abort "-----\nCannot find libmysql.a\n----" unless have_library('libmysql')
+    abort "-----\nCannot link to libmysql.a (my_init)\n----" unless have_func('my_init')
+  end
 
   # Vendor libmysql.dll
   vendordll = File.expand_path('../../../vendor/libmysql.dll', __FILE__)

mysql2.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
   s.test_files = `git ls-files spec examples`.split
 
   # tests
-  s.add_development_dependency 'rake-compiler', '~> 0.8.1'
+  s.add_development_dependency 'rake-compiler', '~> 0.9.5'
   s.add_development_dependency 'rake', '~> 0.9.3'
   s.add_development_dependency 'rspec', '~> 2.8.0'
 end