/usr/include/newlib/sys/string.h is in libnewlib-dev 2.4.0.20160527-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | /* This is a dummy <sys/string.h> used as a placeholder for
systems that need to have a special header file. */
|