linux-user: strace now handles unshare syscall args correctly

Syscall unshare did not have custom print function for strace, but it's argument is same as flags in clone syscall, so it can be easily implemented.
Also updated missing flags from clone_flags.

Signed-off-by: Matus Kysel <mkysel@tachyum.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210406144203.1020598-1-mkysel@tachyum.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/linux-user/strace.list b/linux-user/strace.list
index 084048a..3b7c155 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -1573,7 +1573,7 @@
 { TARGET_NR_unlinkat, "unlinkat" , NULL, print_unlinkat, NULL },
 #endif
 #ifdef TARGET_NR_unshare
-{ TARGET_NR_unshare, "unshare" , NULL, NULL, NULL },
+{ TARGET_NR_unshare, "unshare" , NULL, print_unshare, NULL },
 #endif
 #ifdef TARGET_NR_userfaultfd
 { TARGET_NR_userfaultfd, "userfaultfd" , NULL, NULL, NULL },