Add note about seemingly double relocation of the linker

Change-Id: I1775bf0166f255cc84f41c5d3077e94d7005d2c6
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index 6ccd75b..74cd517 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -722,6 +722,8 @@
   tmp_linker_so.set_linker_flag();
 
   if (!tmp_linker_so.prelink_image()) __linker_cannot_link(args.argv[0]);
+  // There is special logic in soinfo::relocate to avoid duplicating the
+  // relocations we did in relocate_linker().
   if (!tmp_linker_so.link_image(SymbolLookupList(&tmp_linker_so), &tmp_linker_so, nullptr, nullptr)) __linker_cannot_link(args.argv[0]);
 
   return __linker_init_post_relocation(args, tmp_linker_so);