lfs_util: fix assert support in Zephyr installation with newlib

The standard library header in Zephyr minimal libc provides an assert
function that pulls in __ASSERT_NO_MSG.  Newlib does not.  Explicitly
bring in the file that provides the Zephyr assert infrastructure.

Upstream-Status: Inappropriate [Zephyr-specific]
Signed-off-by: Peter A. Bigot <pab@pabigot.com>

lfs_util.h

@@ -29,7 +29,11 @@
 #include <stdlib.h>
 #endif
 #ifndef LFS_NO_ASSERT
+#ifdef __ZEPHYR__
+#include <sys/__assert.h>
+#else  /* __ZEPHYR__ */
 #include <assert.h>
+#endif  /* __ZEPHYR__ */
 #endif
 
 #if !defined(LFS_NO_DEBUG) || \