vmbase: Define .image_footer linker section

Replace the runtime memory reservation for the footer with a linker
defined placeholder. Keep this uniform across the clients instead of
making it specific for the pvmfw.

Note: no functional change intended.

Bug: 377276983
Test: m {pvmfw,rialto,vmbase_example_{bios,kernel}}_bin
Change-Id: I46ca02f68af6e0c135a1b6bf9f0701388ca9a445
diff --git a/libs/libvmbase/src/layout.rs b/libs/libvmbase/src/layout.rs
index 2f710ef..a8f7827 100644
--- a/libs/libvmbase/src/layout.rs
+++ b/libs/libvmbase/src/layout.rs
@@ -70,6 +70,11 @@
     linker_region!(rodata_begin, rodata_end)
 }
 
+/// Region which may contain a footer appended to the binary at load time.
+pub fn image_footer_range() -> Range<VirtualAddress> {
+    linker_region!(image_footer_begin, image_footer_end)
+}
+
 /// Initialised writable data.
 pub fn data_range() -> Range<VirtualAddress> {
     linker_region!(data_begin, data_end)