shellcheck: Fix SC2143

  SC2143 (style): Use ! grep -q instead of comparing output with
  [ -z .. ].

Not a bug.

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-ID: <20240406123833.406488-8-npiggin@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/scripts/arch-run.bash b/scripts/arch-run.bash
index 42cc27a..f8aa5da 100644
--- a/scripts/arch-run.bash
+++ b/scripts/arch-run.bash
@@ -61,7 +61,11 @@
 		# Even when ret==1 (unittest success) if we also got stderr
 		# logs, then we assume a QEMU failure. Otherwise we translate
 		# status of 1 to 0 (SUCCESS)
-		if [ -z "$(echo "$errors" | grep -vi warning)" ]; then
+	        if [ "$errors" ]; then
+			if ! grep -qvi warning <<<"$errors" ; then
+				ret=0
+			fi
+		else
 			ret=0
 		fi
 	fi