feat(ci): build DTBs in the archive directory

They may conflict otherwise if multiple jobs try to build the same one
simultaneously.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I79f7e63cd95c59106a4d828a1930744fd6edbc9c
diff --git a/fvp_utils.sh b/fvp_utils.sh
index fe76023..1bca9dd 100644
--- a/fvp_utils.sh
+++ b/fvp_utils.sh
@@ -145,7 +145,7 @@
 get_dtb() {
 	local dtb_type="${dtb_type:?}"
 	local dtb_url
-	local dtb_saveas="$workspace/dtb.bin"
+	local dtb_saveas="$archive/dtb.bin"
 	local cc="$(get_tf_opt CROSS_COMPILE)"
 	local pp_flags="-P -nostdinc -undef -x assembler-with-cpp"
 
@@ -158,11 +158,11 @@
 		*)
 			# Preprocess DTS file
 			${cc}gcc -E ${pp_flags} -I"$tf_root/fdts" -I"$tf_root/include" \
-				-o "$workspace/${dtb_type}.pre.dts" \
+				-o "$archive/${dtb_type}.pre.dts" \
 				"$tf_root/fdts/${dtb_type}.dts"
 			# Generate DTB file from DTS
 			dtc -I dts -O dtb \
-				"$workspace/${dtb_type}.pre.dts" -o "$dtb_saveas"
+				"$archive/${dtb_type}.pre.dts" -o "$dtb_saveas"
 	esac
 
 	archive_file "$dtb_saveas"