argv: move flags_only to cli/args

Library/Homebrew/cli/args.rb

@@ -28,6 +28,14 @@ def options_only
             .map(&method(:to_cli_option))
             .select { |arg| arg.start_with?("-") }
       end
+
+      def flags_only
+        to_h.keys
+            .map(&:to_s)
+            .reject { |name| %w[argv remaining].include?(name) }
+            .map(&method(:to_cli_option))
+            .select { |arg| arg.start_with?("--") }
+      end
     end
   end
 end

Library/Homebrew/cmd/upgrade.rb

@@ -162,7 +162,7 @@ def upgrade_formula(f)
       tab = Tab.for_keg(keg)
     end
 
-    build_options = BuildOptions.new(Options.create(ARGV.flags_only), f.options)
+    build_options = BuildOptions.new(Options.create(Homebrew.args.flags_only), f.options)
     options = build_options.used_options
     options |= f.build.used_options
     options &= f.options

Library/Homebrew/reinstall.rb

@@ -16,7 +16,7 @@ def reinstall_formula(f, build_from_source: false)
       backup keg
     end
 
-    build_options = BuildOptions.new(Options.create(ARGV.flags_only), f.options)
+    build_options = BuildOptions.new(Options.create(Homebrew.args.flags_only), f.options)
     options = build_options.used_options
     options |= f.build.used_options
     options &= f.options

Library/Homebrew/test/cli/parser_spec.rb

@@ -225,5 +225,10 @@
       parser.parse(["--foo", "-vds", "a", "b", "cdefg"])
       expect(Homebrew.args.options_only).to eq %w[--foo -v -d -s]
     end
+
+    it "#flags_only" do
+      parser.parse(["--foo", "-vds", "a", "b", "cdefg"])
+      expect(Homebrew.args.flags_only).to eq %w[--foo]
+    end
   end
 end