Use ARGV.env

Library/Homebrew/build.rb

@@ -81,8 +81,9 @@ class Build
 
   def pre_superenv_hacks
     # Allow a formula to opt-in to the std environment.
-    ARGV.unshift '--env=std' if (f.env.std? or deps.any? { |d| d.name == 'scons' }) and
-      not ARGV.include? '--env=super'
+    if (f.env.std? || deps.any? { |d| d.name == "scons" }) && ARGV.env != "super"
+      ARGV.unshift "--env=std"
+    end
   end
 
   def expand_reqs

Library/Homebrew/extend/ENV.rb

@@ -6,7 +6,7 @@ require 'extend/ENV/super'
 def superenv?
   return false if MacOS::Xcode.without_clt? && MacOS.sdk_path.nil?
   return false unless Superenv.bin && Superenv.bin.directory?
-  return false if ARGV.include? "--env=std"
+  return false if ARGV.env == "std"
   true
 end