No longer call ENV.userpaths! in requirements

Instead we use which with a custom PATH.

Library/Homebrew/requirement.rb

@@ -94,6 +94,10 @@ class Requirement
     end
   end
 
+  def which(cmd)
+    super(cmd, ORIGINAL_PATHS.join(File::PATH_SEPARATOR))
+  end
+
   class << self
     attr_rw :fatal, :build, :default_formula
 
@@ -118,10 +122,7 @@ class Requirement
       if instance_variable_defined?(:@satisfied)
         @satisfied
       elsif @options[:build_env]
-        ENV.with_build_environment do
-          ENV.userpaths!
-          yield @proc
-        end
+        ENV.with_build_environment { yield @proc }
       else
         yield @proc
       end

Library/Homebrew/test/test_requirement.rb

@@ -50,12 +50,10 @@ class RequirementTests < Test::Unit::TestCase
 
   def test_satisfy_sets_up_build_env_by_default
     req = Class.new(Requirement) do
-      env :userpaths
       satisfy { true }
     end.new
 
     ENV.expects(:with_build_environment).yields.returns(true)
-    ENV.expects(:userpaths!)
 
     assert req.satisfied?
   end
@@ -66,7 +64,6 @@ class RequirementTests < Test::Unit::TestCase
     end.new
 
     ENV.expects(:with_build_environment).never
-    ENV.expects(:userpaths!).never
 
     assert req.satisfied?
   end
@@ -78,7 +75,6 @@ class RequirementTests < Test::Unit::TestCase
     end.new
 
     ENV.expects(:with_build_environment).yields.returns(which_path)
-    ENV.expects(:userpaths!)
     ENV.expects(:append).with("PATH", which_path.parent, ":")
 
     req.satisfied?