fix platform derivation and some tests

lib/arm/arm_platform.rb

@@ -1,6 +1,6 @@
 require_relative "translator"
 module Arm
-  class ArmPlatform
+  class ArmPlatform < Risc::Platform
     def translator
       Translator.new
     end

lib/risc/interpreter_platform.rb

@@ -1,6 +1,6 @@
 
 module Risc
-  class InterpreterPlatform
+  class InterpreterPlatform < Platform
     def translator
       IdentityTranslator.new
     end

lib/risc/linker.rb

@@ -13,7 +13,13 @@ module Risc
     include Util::Logging
     log_level :info
 
-    def initialize
+    def initialize(platform)
+      if(platform.is_a?(Symbol))
+        platform = platform.to_s.capitalize
+        platform = Risc::Platform.for(platform)
+      end
+      raise "Platform must be platform, not #{platform.class}" unless platform.is_a?(Platform)
+      @platform = platform
       @risc_init = nil
       @constants = []
     end

lib/rubyx/rubyx_compiler.rb

@@ -27,9 +27,9 @@ module RubyX
     def ruby_to_binary(platform = :arm)
       Parfait.boot!
       Risc.boot!
-      assemblers = ruby_to_mom(platform)
+      assemblers = ruby_to_mom
       puts "Assemblers #{assemblers}"
-      linker = Linker.new
+      linker = Risc::Linker.new(platform)
       linker.position_all
       linker.create_binary
     end