Add more modern build script for kernel and disk image based on osdev Bare Bones template

GRUB is not identifying the kernel as multiboot compatible. Possibly
because I am using x86_64 instead of i686. Need to investigate further.

Rsconscript

@@ -1,3 +1,71 @@
 configure do
   check_c_compiler "x86_64-elf-gcc", on_fail: "Install cross compiler from x86_64-cross directory"
+  check_program "genext2fs"
+  check_program "grub-mkstandalone"
+  check_program "mformat", on_fail: "Install the mtools package"
+end
+
+build do
+  require "tmpdir"
+
+  # EFI (w/ GRUB) partition size (MiB)
+  EFI_PART_SIZE = 8
+  # HOS partition size (MiB)
+  HOS_PART_SIZE = 4
+
+  class Image < Builder
+    def run(options)
+      unless @cache.up_to_date?(@target, nil, @sources, @env)
+        print_run_message("Generating disk image #{@target}", nil)
+        Dir.mktmpdir do |tmpdir|
+          # Build a standalone GRUB.
+          File.open("#{tmpdir}/grub.cfg", "wb") do |fh|
+            fh.write(<<EOF)
+insmod part_gpt
+configfile (hd0,gpt2)/grub.cfg
+EOF
+          end
+          system(*%W[grub-mkstandalone -O x86_64-efi -o #{tmpdir}/BOOTX64.EFI boot/grub/grub.cfg=#{tmpdir}/grub.cfg])
+          # Create EFI partition.
+          system(*%W[dd if=/dev/zero of=#{tmpdir}/efi.part bs=1M count=#{EFI_PART_SIZE}], err: "/dev/null")
+          system(*%W[mformat -i #{tmpdir}/efi.part ::])
+          system(*%W[mmd -i #{tmpdir}/efi.part ::/EFI])
+          system(*%W[mmd -i #{tmpdir}/efi.part ::/EFI/BOOT])
+          system(*%W[mcopy -i #{tmpdir}/efi.part #{tmpdir}/BOOTX64.EFI ::/EFI/BOOT])
+          # Create ext2 HOS partition.
+          FileUtils.mkdir_p("#{tmpdir}/ext2")
+          @sources.each do |source|
+            FileUtils.cp(source, "#{tmpdir}/ext2")
+          end
+          File.open("#{tmpdir}/ext2/grub.cfg", "wb") do |fh|
+            fh.write(<<EOF)
+insmod part_gpt
+insmod multiboot
+set root=(hd0,gpt2)
+multiboot /hos.elf
+EOF
+          end
+          system(*%W[genext2fs -b #{HOS_PART_SIZE * 1024} -d #{tmpdir}/ext2 #{tmpdir}/ext2.part])
+          # Create full disk image.
+          system(*%W[dd if=/dev/zero of=#{@target} bs=1M count=#{EFI_PART_SIZE + HOS_PART_SIZE + 2}], err: "/dev/null")
+          system(*%W[parted -s #{@target} mklabel gpt])
+          system(*%W[parted -s #{@target} mkpart efi 1MiB #{EFI_PART_SIZE + 1}MiB])
+          system(*%W[parted -s #{@target} mkpart hos #{EFI_PART_SIZE + 1}MiB #{EFI_PART_SIZE + HOS_PART_SIZE + 1}MiB])
+          system(*%W[dd if=#{tmpdir}/efi.part of=#{@target} bs=1M seek=1 conv=notrunc], err: "/dev/null")
+          system(*%W[dd if=#{tmpdir}/ext2.part of=#{@target} bs=1M seek=#{1 + EFI_PART_SIZE} conv=notrunc], err: "/dev/null")
+        end
+        @cache.register_build(@target, nil, @sources, @env)
+      end
+      true
+    end
+  end
+
+  Environment.new do |env|
+    env.add_builder(Image)
+    env["CCFLAGS"] += %w[-ffreestanding -Wall -O2]
+    env["LDFLAGS"] += %w[-ffreestanding -nostdlib -T src/link.ld]
+    env["LIBS"] += %w[gcc]
+    env.Program("^/hos.elf", glob("src/**/*.{S,c}"))
+    env.Image("build/hos.img", %w[^/hos.elf])
+  end
 end