BUILD/MINOR: syscall: add definition of NR_accept4 for ARM

This platform was not covered and older libc do not provide accept4().
diff --git a/include/common/syscall.h b/include/common/syscall.h
index 659b0ca..0b1ccd6 100644
--- a/include/common/syscall.h
+++ b/include/common/syscall.h
@@ -132,6 +132,8 @@
 #define __NR_accept4            288
 #elif defined(__sparc__) || defined(__sparc64__)
 #define __NR_accept4            323
+#elif defined(__arm__) || defined(__thumb__)
+#define __NR_accept4            (__NR_SYSCALL_BASE+366)
 #else
 #define ACCEPT4_USE_SOCKETCALL    1
 #ifndef SYS_ACCEPT4