audit: recognize options used with 'ARGV.flag?'

A few formula use ARGV.flag? instead of ARGV.include?. This made `audit`
recognize a few undocumented instances of a '--devel' option, but we can
just ignore that like '--HEAD' for now, and change the behavior if we
decide they need to be documented explicitly in each formula.

cf. Homebrew/homebrew#7456.

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

Library/Homebrew/cmd/audit.rb

@@ -124,7 +124,7 @@ def audit_formula_options f, text
 
   # Find possible options
   options = []
-  text.scan(/ARGV\.include\?[ ]*\(?(['"])(.+?)\1/) { |m| options << m[1] }
+  text.scan(/ARGV\.(include|flag)\?[ ]*\(?(['"])(.+?)\2/) { |m| options << m[2] }
   options.reject! {|o| o.include? "#"}
   options.uniq!
 
@@ -140,7 +140,7 @@ def audit_formula_options f, text
 
   if options.length > 0
     options.each do |o|
-      next if o == '--HEAD'
+      next if o == '--HEAD' || o == '--devel'
       problems << " * Option #{o} is not documented" unless documented_options.include? o
     end
   end