formula_installer: check pour from requirements.

Library/Homebrew/formula_installer.rb

@@ -55,6 +55,14 @@ class FormulaInstaller
     return true if f.local_bottle_path
     return false unless f.bottle && f.pour_bottle?
 
+    f.requirements.each do |req|
+      next if req.optional? || req.pour_bottle?
+      if install_bottle_options[:warn]
+        ohai "Building source; bottle blocked by #{req} requirement"
+      end
+      return false
+    end
+
     unless f.bottle.compatible_cellar?
       if install_bottle_options[:warn]
         opoo "Building source; cellar of #{f}'s bottle is #{f.bottle.cellar}"