Update LinuxRandomUuidSysctlRandomSeed.c
Sysctl has been deprecated for some time, and current gcc is aggressive about flagging uses of it, causing cjdns builds to fail. This patch simply removes sysctl.h and sysctl calls when SYS_getrandom is defined. Any linux system that is modern enough to make a stink about sysctl calls, is also modern enough to have getrandom.