Fix passing multiple switches as a single word to the build

Fixes Homebrew/homebrew#17434.

Library/Homebrew/options.rb

@@ -1,3 +1,5 @@
+require 'set'
+
 class Option
   include Comparable
 
@@ -33,6 +35,8 @@ class Option
 
   def split_name(name)
     case name
+    when /^[a-zA-Z]$/
+      [name, "-#{name}"]
     when /^-[a-zA-Z]$/
       [name[1..1], name]
     when /^--(.+)$/
@@ -101,8 +105,16 @@ class Options
     case arg
     when self then arg
     when Option then new << arg
-    when Array then new(arg.map { |a| Option.new(a.to_s) })
-    else raise TypeError, "Cannot convert #{arg.inspect} to Options"
+    when Array
+      opts = arg.map do |arg|
+        case arg
+        when /^-[^-]+$/ then arg[1..-1].split(//)
+        else arg
+        end
+      end.flatten
+      new(opts.map { |o| Option.new(o) })
+    else
+      raise TypeError, "Cannot convert #{arg.inspect} to Options"
     end
   end
 end

Library/Homebrew/test/test_options.rb

@@ -140,4 +140,11 @@ class OptionsTests < Test::Unit::TestCase
   def test_coerce_raises_for_inappropriate_types
     assert_raises(TypeError) { Options.coerce(1) }
   end
+
+  def test_coerce_splits_multiple_switches_with_single_dash
+    array = %w{-vd}
+    verbose = Option.new("-v")
+    debug = Option.new("-d")
+    assert_equal [verbose, debug].sort, Options.coerce(array).to_a.sort
+  end
 end