procd: fix early killing of /sbin/init on airoha aarch64.
See targets!1061 (merged), https://dev.iopsys.eu/feed/airoha/-/merge_requests/153 and https://dev.iopsys.eu/airoha/linux/-/commits/mkshevetskiy-an7581 as well.
By unknown reason
path = buf2 + sprintf(buf2, "%s/", path);
terminates /sbin/init on airoha aarch64 with musl. As result the kernel tries to kill process with pid = 1 and dies on it. Resolve this issue with equivalent code but not using sprintf().
Edited by Mikhail Kshevetskiy