fs_shell: Detect 64-bit by comparing LONG_MAX and INT_MAX.

This is how we do it within the kernel itself. Should fix build of fs_shell
on 64-bit platforms that are not x86.

src/tools/fs_shell/vfs.cpp

@@ -3697,7 +3697,7 @@ common_lock_node(int fd, bool kernel)
 
 	// We need to set the locking atomically - someone
 	// else might set one at the same time
-#ifdef __x86_64__
+#if LONG_MAX == INT_MAX
 	if (fssh_atomic_test_and_set64((int64_t *)&vnode->mandatory_locked_by,
 			(fssh_addr_t)descriptor, 0) != 0)
 #else