vmbase: Move linker to aarch64

This commit move aarch64 linker definition to arch specific module.

Bug: 362733888
Test: m libvmbase

Change-Id: Ib00cbaa981c948e626d58a0f0d818d4ec1f4ceb3
diff --git a/guest/vmbase_example/src/main.rs b/guest/vmbase_example/src/main.rs
index b7d2f95..8723a55 100644
--- a/guest/vmbase_example/src/main.rs
+++ b/guest/vmbase_example/src/main.rs
@@ -30,11 +30,12 @@
 use log::{debug, error, info, trace, warn, LevelFilter};
 use spin::mutex::SpinMutex;
 use vmbase::{
+    arch::linker,
     bionic, configure_heap,
     fdt::pci::PciInfo,
     generate_image_header,
     layout::crosvm::FDT_MAX_SIZE,
-    linker, logger, main,
+    logger, main,
     memory::{deactivate_dynamic_page_tables, map_data, SIZE_64KB},
 };