libc/minimal: Add stub 'sys/lock.h'

This file is explicitly included by the espressif hal module. It's an
internal file provided by picolibc and newlib. Provide a stub to let
code designed for those to work with the minimal C library.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

lib/libc/minimal/include/sys/lock.h

@@ -0,0 +1,7 @@
+/*
+ * Copyright The Zephyr Project Contributors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/* empty file for newlib compatibility */