fix(ci): respect retain_paths when downloading llvm

Most workstations have LLVM installed. Most developers will have
retain_paths set which is meant to skip some downloads. Respect this for
the llvm download so that CI can run more quickly locally.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I14c8de37613067bc0a9187411504d8ccd873bd3b
diff --git a/utils.sh b/utils.sh
index b154773..364d0b6 100644
--- a/utils.sh
+++ b/utils.sh
@@ -475,7 +475,11 @@
 	archive="${2:-"$workspace/llvm.tar.xz"}"
 	target_dir="${3:-$llvm_dir}"
 
-	if is_arm_jenkins_env || upon "$local_ci"; then
+	if upon "$retain_paths"; then
+		return
+	fi
+
+	if upon "$local_ci"; then
 		url="$link" saveas="$archive" fetch_file
 		mkdir -p $target_dir
 		extract_tarball $archive $target_dir --strip-components=1 -k