There is no installing Linux libraries in the BSD here; this file is in the
GNU C library's contents/compiler. This is a set of constants on the sticky
bit permissions management.

Most likely what is happening is that on Linux the file is #included by some
other #include file. To see if this is the case do the following. In the code
(the file you mentioned that uses the constant) put this:

#ifdef _SYS_STAT_H
# warning "My missing file has already been included"
#endif

Here is how to fix your code to compile properly. In the place where this file
is included, use this:

#ifdef __USE_BSD 
# include <sys/stat.h>
#endif

You are done.