add initial source and build system

Rsconscript

@@ -0,0 +1,11 @@
+build do
+  Environment.new do |env|
+    env["CC"] = "x86_64-w64-mingw32-gcc"
+    env["CPPPATH"] += %w[/usr/include/efi /usr/include/efi/x86_64]
+    env["CFLAGS"] += %w[-ffreestanding]
+    env["LDFLAGS"] += %w[-nostdlib -Wl,-dll -shared -Wl,--subsystem,10 -e efi_main]
+    env["LIBS"] += %w[gcc]
+    env["sources"] = glob("*.c")
+    env.Program("^/BOOTX64.EFI", "${sources}")
+  end
+end