Delay loading Pathname until we absolutely need it

Library/ENV/4.3/xcrun

@@ -4,15 +4,6 @@
 # But many build-systems expect it to work. This fixes that.
 # NOTE only works if the build-tool calls xcrun without a path prefixed!
 
-$:.unshift "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8"
-require "pathname"
-
-def canonical_dirname path
-  Pathname.new(path).dirname.realpath.to_s
-end
-
-SUPERBIN = canonical_dirname(__FILE__)
-
 # Some build tools are stupid and still set DEVELOPER_DIR to old /Developer
 ENV.delete "DEVELOPER_DIR"
 
@@ -25,6 +16,15 @@ if File.exist?("/usr/bin/#{ARGV.first}")
   exec "/usr/bin/#{ARGV.shift}", *ARGV unless sdkroot and File.directory? sdkroot
 end
 
+$:.unshift "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8"
+require "pathname"
+
+def canonical_dirname path
+  Pathname.new(path).dirname.realpath.to_s
+end
+
+SUPERBIN = canonical_dirname(__FILE__)
+
 def try path
   exec path, *ARGV if File.executable?(path) && canonical_dirname(path) != SUPERBIN
 end