build kernel .size file on build

Rsconscript

@@ -109,6 +109,19 @@ EOF
     end
   end
 
+  class Size < Builder
+    def run(options)
+      if @command
+        finalize_command
+      else
+        @vars["_SOURCES"] = @sources
+        @vars["_TARGET"] = @target
+        command = @env.build_command(%w[${SIZE} ${_SOURCES}], @vars)
+        standard_command("Size <target>#{@target}<reset>", command, stdout: @target)
+      end
+    end
+  end
+
   # FontGen Environment
   Environment.new(use: "freetype") do |env|
     env["CC"] = "gcc"
@@ -120,16 +133,19 @@ EOF
     env.add_builder(EfiImage)
     env.add_builder(BiosImage)
     env.add_builder(FontGen)
+    env.add_builder(Size)
+    env["OBJDUMP"] = "i686-elf-objdump"
+    env["SIZE"] = "i686-elf-size"
     env["CCFLAGS"] += %w[-ffreestanding -Wall -O2]
     env["LDFLAGS"] += %w[-ffreestanding -nostdlib -T src/link.ld]
     env["LDFLAGS"] += %W[-Wl,-Map,${_TARGET}.map]
     env["LIBS"] += %w[gcc]
-    env["OBJDUMP"] = "i686-elf-objdump"
     env.FontGen("^/kfont/kfont.c", "font/Hack-Regular.ttf")
     env["CPPPATH"] += ["#{env.build_root}/kfont"]
     env.Program("^/hos.elf", glob("src/**/*.{S,c}") + ["^/kfont/kfont.c"])
     env.depends("#{env.build_root}/hos.elf", "src/link.ld")
     env.Disassemble("^/hos.elf.txt", "^/hos.elf")
+    env.Size("^/hos.elf.size", "^/hos.elf")
     env.EfiImage("build/hos-efi.img", %w[^/hos.elf])
     env.BiosImage("build/hos.img", %w[^/hos.elf])
   end