Use xcrun; Ensure clang is the default compiler with Xcode 4.3

Using xcrun as a proxy to execute the compiler tools is per its design. This means you can't treat ENV['CC'] as a path anymore, but I think I found the cases this was being expected and corrected them. It was not proper anyway to assume the variable was a path, it can be anything. Like a proxy. Like xcrun.

Also more thoroughly clear ENV.

1 files changed, 5 insertions, 3 deletions

diff --git a/Library/Homebrew/cmd/--env.rb b/Library/Homebrew/cmd/--env.rb
index f8dcb0f47..7d9796061 100644
--- a/Library/Homebrew/cmd/--env.rb
+++ b/Library/Homebrew/cmd/--env.rb
@@ -18,9 +18,11 @@ module Homebrew extend self
       value = env[k]
       if value
         results = value
-        if File.exists? value and File.symlink? value
-          target = Pathname.new(value)
-          results += " => #{target.realpath}"
+        if value =~ %r{^/usr/bin/xcrun (.*)}
+          path = `/usr/bin/xcrun -find #{$1}`
+          results += " => #{path}"
+        elsif File.exists? value and File.symlink? value
+          results += " => #{Pathname.new(value).realpath}"
         end
         puts "#{k}: #{results}"
       end