revert last two commits. vfork cannot be used in subroutine,

it trashes stack on return

archival/libunarchive/open_transformer.c

@@ -20,7 +20,16 @@ int FAST_FUNC open_transformer(int src_fd,
 
 	xpiped_pair(fd_pipe);
 
-	pid = BB_MMU ? xfork() : xvfork();
+#if BB_MMU
+	pid = fork();
+	if (pid == -1)
+		bb_perror_msg_and_die("can't fork");
+#else
+	pid = vfork();
+	if (pid == -1)
+		bb_perror_msg_and_die("can't vfork");
+#endif
+
 	if (pid == 0) {
 		/* child process */
 		close(fd_pipe.rd); /* We don't want to read from the parent */