Include mman.h before disabling non-POSIX headers
The new use of MAP_ANONYMOUS in rts/sm/Storage.c added in ddb152d5 is not compatible with the extant #include "PosixSource.h"
which limits system headers to export only POSIX definitions. In particular, on FreeBSD and Darwin systems, <sys/mman.h>
does not define either of MAP_ANON
or MAP_ANONYMOUS
when "PosixSource.h"
is included first.
While we could simply stop limiting rts/sm/Storage.c
to POSIX features, for just one non-POSIX macro (at least per FreeBSD and Darwin) it is simple to include <sys/mman.h>
first.
Closes: #19456 (closed)