bug#45198: 28.0.50; Sandbox mode

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sat, 19 Dec 2020 23:22:08 +0100
> Cc: Bastien <bzg@gnu.org>, 45198@debbugs.gnu.org,
>  João Távora <joaotavora@gmail.com>
> 
> diff --git a/configure.ac b/configure.ac
> index 087dd67e18..cb698e34fe 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -4186,6 +4186,11 @@ AC_DEFUN
>  
>  AC_CHECK_HEADERS([linux/seccomp.h])
>  
> +LIBSECCOMP=
> +AC_CHECK_HEADER([seccomp.h],
> +  [AC_CHECK_LIB([seccomp], [seccomp_init], [LIBSECCOMP=-lseccomp])])
> +AC_SUBST([LIBSECCOMP])
> +

Please also add this to the list in EMACS_CONFIG_FEATURES.