unix: check for EXDEV in uv__fs_sendfile()

copy_file_range will not work when in_fd and out_fd
are not on the same mounted filesystem (pre Linux 5.3).

Refs: nodejs/node#37284
PR-URL: libuv#3108
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>

src/unix/fs.c

@@ -926,8 +926,10 @@ static ssize_t uv__fs_sendfile(uv_fs_t* req) {
           /* ENOSYS - it will never work */
           errno = 0;
           copy_file_range_support = 0;
-        } else if (r == -1 && errno == ENOTSUP) {
+        } else if (r == -1 && (errno == ENOTSUP || errno == EXDEV)) {
           /* ENOTSUP - it could work on another file system type */
+          /* EXDEV - it will not work when in_fd and out_fd are not on the same
+                     mounted filesystem (pre Linux 5.3) */
           errno = 0;
         } else {
           goto ok;