ARGV: use include? for --HEAD

ARGV.build_head? will return true if the typo '-HEAD' is passed because
it uses flag? to detect the option. However, we only filter the exact
spelling of '--HEAD' in ARGV.filter_for_dependencies, and thus the HEAD
property is undesirably passed to deps during installation.

Since we never advertised '-H' as a valid short option for '--HEAD',
just use include? instead of flag?.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Library/Homebrew/extend/ARGV.rb

@@ -89,7 +89,7 @@ module HomebrewArgvExtension
   end
 
   def build_head?
-    flag? '--HEAD'
+    include? '--HEAD'
   end
 
   def build_devel?