Find xcrun if user doesn't ever install Xcode 4.3 helper tools

Library/Homebrew/cmd/--env.rb

@@ -18,8 +18,8 @@ module Homebrew extend self
       value = env[k]
       if value
         results = value
-        if value =~ %r{^/usr/bin/xcrun (.*)}
-          path = `/usr/bin/xcrun -find #{$1}`
+        if value =~ /^[^\s]*xcrun (.*)/
+          path = `#{MacOS.xcrun} -find #{$1}`
           results += " => #{path}"
         elsif File.exists? value and File.symlink? value
           results += " => #{Pathname.new(value).realpath}"

Library/Homebrew/extend/ENV.rb

@@ -89,7 +89,7 @@ module HomebrewEnvExtension
   def xcrun tool
     if File.executable? "/usr/bin/#{tool}"
       "/usr/bin/#{tool}"
-    elsif system "/usr/bin/xcrun -find #{tool} 2>1 1>/dev/null"
+    elsif system "#{MacOS.xcrun} -find #{tool} 2>1 1>/dev/null"
       # xcrun was provided first with Xcode 4.3 and allows us to proxy
       # tool usage thus avoiding various bugs
       "/usr/bin/xcrun #{tool}"
@@ -106,10 +106,10 @@ module HomebrewEnvExtension
 
   # if your formula doesn't like CC having spaces use this
   def expand_xcrun
-    ENV['CC'] =~ %r{/usr/bin/xcrun (.*)}
-    ENV['CC'] = `/usr/bin/xcrun -find #{$1}`.chomp if $1
-    ENV['CXX'] =~ %r{/usr/bin/xcrun (.*)}
-    ENV['CXX'] = `/usr/bin/xcrun -find #{$1}`.chomp if $1
+    ENV['CC'] =~ %r{#{MacOS.xcrun} (.*)}
+    ENV['CC'] = `#{MacOS.xcrun} -find #{$1}`.chomp if $1
+    ENV['CXX'] =~ %r{#{MacOS.xcrun} (.*)}
+    ENV['CXX'] = `#{MacOS.xcrun} -find #{$1}`.chomp if $1
   end
 
   def gcc args = {}
@@ -126,7 +126,7 @@ module HomebrewEnvExtension
       raise "GCC could not be found" if not File.exist? ENV['CC']
     end
 
-    if not ENV['CC'] =~ %r{^/usr/bin/xcrun}
+    if not ENV['CC'] =~ /^[^\s]*xcrun /
       raise "GCC could not be found" if Pathname.new(ENV['CC']).realpath.to_s =~ /llvm/
     end
 

Library/Homebrew/utils.rb

@@ -266,8 +266,16 @@ module MacOS extend self
     end
   end
 
+  def xcrun
+    @xcrun ||= begin
+      path = "#{xcode_prefix}/usr/bin/xcrun"
+      path = "xcrun" unless File.file? path # just in case
+      path
+    end
+  end
+
   def default_cc
-    cc = `/usr/bin/xcrun -find cc 2> /dev/null`.chomp
+    cc = `#{xcrun} -find cc 2> /dev/null`.chomp
     cc = "#{dev_tools_path}/cc" if cc.empty?
     Pathname.new(cc).realpath.basename.to_s rescue nil
   end