Fix Lightrec build on Windows and Linux

Fix Lightrec build on Windows and Linux

Some distributions of Linux don't have the MFD_HUGETLB flag in
<linux/memfd.h>, probably because their kernel headers installed are too
old. In that case, we locally define MFD_HUGETLB to the value it should
have.

On Windows, the HAVE_MMAP macro set for GNU Lightning was also used in
libretro-common/vfs/vfs_implementation.c, causing build issues. Address
this problem by only defining HAVE_MMAP for Lightning source files.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>