We have patched the ndk header to include getsid().

diff -u -r ../busybox-1.22.1/libbb/missing_syscalls.c ./libbb/missing_syscalls.c
--- ../busybox-1.22.1/libbb/missing_syscalls.c	2014-01-09 19:15:44.000000000 +0100
+++ ./libbb/missing_syscalls.c	2014-07-08 15:57:13.545408937 +0200
@@ -11,11 +11,6 @@
 #include "libbb.h"
 
 #if defined(ANDROID) || defined(__ANDROID__)
-pid_t getsid(pid_t pid)
-{
-	return syscall(__NR_getsid, pid);
-}
-
 int stime(const time_t *t)
 {
 	struct timeval tv;