Object#instance_exec for Ruby 1.8.6

Not thread safe! But I don't think we care.

We want to evaluate the env DSL block in the context of ENV for asthetic
reasons, but we also want access to methods on the requirement instance.
We can use #instance_exec to pass the requirement itself into the block:

  class Foo < Requirement
    env do |req|
      append 'PATH', req.some_path
    end

    def some_path
      which 'something'
    end
  end

Also add a simplified version of Object#instance_exec for Ruby 1.8.6.

1 files changed, 2 insertions, 2 deletions

diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index 18876f954..60e099977 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -18,9 +18,9 @@ class BuildEnvironment
     @settings.include? :userpaths
   end
 
-  def modify_build_environment
+  def modify_build_environment(context=nil)
     p = @settings.find { |s| Proc === s }
-    ENV.instance_eval(&p) unless p.nil?
+    ENV.instance_exec(context, &p) unless p.nil?
   end
 
   def _dump(*)