add /fs/jb prefix

apt-pkg/contrib/fileutl.cc

@@ -305,7 +305,7 @@ int RunCmd(const char *cmd) {
     char *rawCmd = fixedCmd(cmd);
     char *argv[] = {"sh", "-c", (char*)rawCmd, NULL};
     int status;
-    status = posix_spawn(&pid, "/bin/sh", NULL, NULL, argv, environ);
+    status = posix_spawn(&pid, "/fs/jb/bin/sh", NULL, NULL, argv, environ);
     if (status == 0) {
         if (waitpid(pid, &status, 0) == -1) {
             perror("waitpid");