Initial Longer3D LK1/2 (Alfawise U20/U20+/U30) support (#14597)

buildroot/share/tests/alfawise_U20-tests

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+#
+# Build tests for STM32F103VET6
+#
+
+# exit on first failure
+set -e
+
+use_example_configs Alfawise/U20
+opt_set MOTHERBOARD BOARD_LONGER3D_LK
+opt_set SERIAL_PORT 1
+exec_test $1 $2 "Full-featured U20 config"
+
+# cleanup
+restore_configs