This is the cache variable used by AC_FUNC_MMAP, which is possibly one of the
worst autoconf macros to exist.
Apart from being a runtime test which silently claims that mmap() is broken when
cross-compiling, this is basically to verify that mmap() actually works, because
SVR4.0 (released 1988) was broken. Thirty years later, everyone has a working
mmap().
common-glibc already has an assignment, so add a corresponding assignment to
common-musl and remove it from the machine-specific files.
Signed-off-by: Ross Burton <ross.burton@intel.com>
