Add unshare() syscall.

(cherry-pick of 5467f25f82934d611c60f8bc57a05114f3c1bea0.)

Bug: 6925012
Change-Id: Ic5ea2fbd606311087de05d7a3594df2fa9b2fef9
diff --git a/libc/include/sys/linux-syscalls.h b/libc/include/sys/linux-syscalls.h
index c8a654c..c33dc9f 100644
--- a/libc/include/sys/linux-syscalls.h
+++ b/libc/include/sys/linux-syscalls.h
@@ -155,6 +155,7 @@
 #define __NR_removexattr                  (__NR_SYSCALL_BASE + 235)
 #define __NR_lremovexattr                 (__NR_SYSCALL_BASE + 236)
 #define __NR_statfs64                     (__NR_SYSCALL_BASE + 266)
+#define __NR_unshare                      (__NR_SYSCALL_BASE + 337)
 #define __NR_nanosleep                    (__NR_SYSCALL_BASE + 162)
 #define __NR_clock_gettime                (__NR_SYSCALL_BASE + 263)
 #define __NR_clock_settime                (__NR_SYSCALL_BASE + 262)
@@ -318,6 +319,7 @@
 #define __NR_renameat                     (__NR_SYSCALL_BASE + 302)
 #define __NR_fchmodat                     (__NR_SYSCALL_BASE + 306)
 #define __NR_faccessat                    (__NR_SYSCALL_BASE + 307)
+#define __NR_unshare                      (__NR_SYSCALL_BASE + 310)
 #define __NR_getcpu                       (__NR_SYSCALL_BASE + 318)
 #define __NR_utimensat                    (__NR_SYSCALL_BASE + 320)
 #define __NR_eventfd2                     (__NR_SYSCALL_BASE + 328)
@@ -444,6 +446,7 @@
 #define __NR_renameat                     (__NR_SYSCALL_BASE + 295)
 #define __NR_fchmodat                     (__NR_SYSCALL_BASE + 299)
 #define __NR_faccessat                    (__NR_SYSCALL_BASE + 300)
+#define __NR_unshare                      (__NR_SYSCALL_BASE + 303)
 #define __NR_getcpu                       (__NR_SYSCALL_BASE + 312)
 #define __NR_ioprio_set                   (__NR_SYSCALL_BASE + 314)
 #define __NR_ioprio_get                   (__NR_SYSCALL_BASE + 315)