refactor: factor LAVA job artefact URLs into an array

This is a simple change that collects the artefact URLs into a single
associative array, rather than keeping them as free variables. This
makes it a bit more obvious that they are related, and also makes them
local to the function (arrays are local by default).

Change-Id: I38afc31f74bc2e7f5674a96881e5c51c725827e3
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/script/lava-templates/fvp-linux.yaml b/script/lava-templates/fvp-linux.yaml
index 96f69fe..a0acc6e 100644
--- a/script/lava-templates/fvp-linux.yaml
+++ b/script/lava-templates/fvp-linux.yaml
@@ -46,7 +46,7 @@
 $(for artefact in "${artefacts[@]:?}"; do
 	cat <<-YAML
       ${artefact:?}:
-        url: ${!artefact:?}
+        url: ${artefact_urls[${artefact}]:?}
 	YAML
 
 	[[ "${artefact:?}" =~ ^(busybox|rootfs)$ ]] && cat <<-YAML