Allow explicit conversion of requirements to deps

Fixes Homebrew/homebrew#19857.

1 files changed, 5 insertions, 0 deletions

diff --git a/Library/Homebrew/dependency.rb b/Library/Homebrew/dependency.rb
index a6905bc37..91def8442 100644
--- a/Library/Homebrew/dependency.rb
+++ b/Library/Homebrew/dependency.rb
@@ -5,6 +5,7 @@ class Dependency
   include Dependable
 
   attr_reader :name, :tags
+  attr_accessor :env_proc
 
   def initialize(name, tags=[])
     @name = name
@@ -54,6 +55,10 @@ class Dependency
     tags << 'universal' if to_formula.build.has_option? 'universal'
   end
 
+  def modify_build_environment
+    env_proc.call unless env_proc.nil?
+  end
+
   class << self
     # Expand the dependencies of dependent recursively, optionally yielding
     # [dependent, dep] pairs to allow callers to apply arbitrary filters to