livepatch/klp-build: improve short-circuit validation

Update SHORT_CIRCUIT behavior to better handle patch validation and
argument processing in later klp-build steps.

Perform patch validation for both step 1 (building original kernel) and
step 2 (building patched kernel) to ensure patches are verified before
any compilation occurs.

Additionally, allow the user to omit input patches when skipping past
step 2.

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/20260310203751.1479229-9-joe.lawrence@redhat.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

scripts/livepatch/klp-build

@@ -220,7 +220,7 @@ process_args() {
 		esac
 	done
 
-	if [[ $# -eq 0 ]]; then
+	if [[ $# -eq 0 ]] && (( SHORT_CIRCUIT <= 2 )); then
 		usage
 		exit 1
 	fi
@@ -791,9 +791,12 @@ build_patch_module() {
 process_args "$@"
 do_init
 
-if (( SHORT_CIRCUIT <= 1 )); then
+if (( SHORT_CIRCUIT <= 2 )); then
 	status "Validating patch(es)"
 	validate_patches
+fi
+
+if (( SHORT_CIRCUIT <= 1 )); then
 	status "Building original kernel"
 	clean_kernel
 	build_kernel