Add a method for retrieving only flags from ARGV

Library/Homebrew/build.rb

@@ -186,7 +186,7 @@ begin
   trap("INT", old_trap)
 
   formula = ARGV.formulae.first
-  options = Options.create(ARGV.options_only)
+  options = Options.create(ARGV.flags_only)
   build   = Build.new(formula, options)
   build.install
 rescue Exception => e

Library/Homebrew/extend/ARGV.rb

@@ -7,6 +7,10 @@ module HomebrewArgvExtension
     select { |arg| arg.start_with?("-") }
   end
 
+  def flags_only
+    select { |arg| arg.start_with?("--") }
+  end
+
   def formulae
     require "formula"
     @formulae ||= downcased_unique_named.map { |name| Formulary.factory(name, spec) }

Library/Homebrew/software_spec.rb

@@ -36,7 +36,7 @@ class SoftwareSpec
     @bottle_specification = BottleSpecification.new
     @patches = []
     @options = Options.new
-    @build = BuildOptions.new(Options.create(ARGV.options_only), options)
+    @build = BuildOptions.new(Options.create(ARGV.flags_only), options)
     @compiler_failures = []
   end
 

Library/Homebrew/test/test_ARGV.rb

@@ -30,6 +30,11 @@ class ArgvExtensionTests < Homebrew::TestCase
     assert_equal %w[--foo -vds], @argv.options_only
   end
 
+  def test_flags_only
+    @argv << "--foo" << "-vds" << "a" << "b" << "cdefg"
+    assert_equal %w[--foo], @argv.flags_only
+  end
+
   def test_empty_argv
     assert_empty @argv.named
     assert_empty @argv.kegs