Fix Fysetc S6 FLASH_PAGE_SIZE and test build (#16560)

buildroot/share/tests/FYSETC_S6-tests

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+#
+# Build tests for FYSETC_S6
+#
+
+# exit on first failure
+set -e
+
+# Build examples
+restore_configs
+use_example_configs FYSETC/S6
+exec_test $1 $2 "FYSETC S6 Example"
+
+# cleanup
+restore_configs