New driver does not compile on macOS

[clementval]

The new driver is making use of a cpp frontend in xcodeml-tools and this does not compile under macOS because it uses posix_fallocate function.

xcodeml-tools/F-FrontEnd-cpp/src/io_cache.cpp:145:17: error: 'posix_fallocate' was not declared in this scope
             if (posix_fallocate(fd, 0, size) != 0)

quick workaround is to add a simple implementation to be able to compile

static int posix_fallocate(int fd, off_t offset, off_t len)
{
    off_t c_test;
    int ret;
    if (!__builtin_saddll_overflow(offset, len, &c_test)) {
        fstore_t store = {F_ALLOCATECONTIG, F_PEOFPOSMODE, 0, offset + len};
        // Try to get a continuous chunk of disk space
        fcntl(fd, F_PREALLOCATE, &store);
        if (ret < 0) {
            // OK, perhaps we are too fragmented, allocate non-continuous
            store.fst_flags = F_ALLOCATEALL;
            ret = fcntl(fd, F_PREALLOCATE, &store);
            if (ret < 0) {
                return ret;
            }
        }
        ret = ftruncate(fd, offset + len);
    } else {
        // offset+len would overflow.
        ret = -1;
    }
    return ret;
}