Move all guid instances into .rodata in our own list.

src/boot/guids.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <efi.h>
+
+int is_guid(EFI_GUID *a, EFI_GUID *b);
+
+#define GUID(dw, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8, name) extern EFI_GUID name
+#include "guids.inc"
+#undef GUID