Add unshare() syscall.

(cherry-pick of 5467f25f82934d611c60f8bc57a05114f3c1bea0.)

Bug: 6925012
Change-Id: Ic5ea2fbd606311087de05d7a3594df2fa9b2fef9
diff --git a/libc/arch-mips/syscalls.mk b/libc/arch-mips/syscalls.mk
index 8c0c4dc..6de0c8f 100644
--- a/libc/arch-mips/syscalls.mk
+++ b/libc/arch-mips/syscalls.mk
@@ -124,6 +124,7 @@
 syscall_src += arch-mips/syscalls/removexattr.S
 syscall_src += arch-mips/syscalls/lremovexattr.S
 syscall_src += arch-mips/syscalls/__statfs64.S
+syscall_src += arch-mips/syscalls/unshare.S
 syscall_src += arch-mips/syscalls/pause.S
 syscall_src += arch-mips/syscalls/gettimeofday.S
 syscall_src += arch-mips/syscalls/settimeofday.S