tfa-next: include bl31.{bin,elf} in archive

Currently collect_build_artefacts() only looks in $tf_build_root for
*.bin/*.elf files to copy into the archive.

Since the Rust bl31 binary and elf files are placed in the rust/target
dir, they are not currently archived by the Jenkins CI.

Sym link bl31.{bin,elf} into $tf_build_root so they can be archived with
the rest.

Change-Id: I9eb16ba4eff1ff1e163367c38afe4231da388016
Signed-off-by: Zachary Leaf <zachary.leaf@arm.com>
diff --git a/script/build_package.sh b/script/build_package.sh
index 07d878d..6538541 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -1543,6 +1543,11 @@
 		# Pre-archive hook
 		call_hook pre_tf_archive
 
+		if upon "$(get_tf_opt RUST)"; then
+			# for archiving into the Jenkins artifacts directory
+			ln -fsr $tf_root/rust/target/bl31.{bin,elf} $tf_build_root
+		fi
+
 		from="$tf_build_root" to="$archive" collect_build_artefacts
 
 		# Post-archive hook