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

diff -u -r ../busybox-1.29.1/libbb/missing_syscalls.c ./libbb/missing_syscalls.c
--- ../busybox-1.29.1/libbb/missing_syscalls.c	2018-07-02 11:23:06.000000000 +0000
+++ ./libbb/missing_syscalls.c	2018-07-22 23:12:25.751499056 +0000
@@ -10,10 +10,6 @@
 #if defined(ANDROID) || defined(__ANDROID__)
 /*# include <linux/timex.h> - for struct timex, but may collide with <time.h> */
 # include <sys/syscall.h>
-pid_t getsid(pid_t pid)
-{
-	return syscall(__NR_getsid, pid);
-}
 
 int stime(const time_t *t)
 {