package/rtty: fix openssl static build with -latomic

Fix the following openssl static build failure with -latomic raised
since bump to version 8.1.0 in commit
7e608885:

/home/autobuild/autobuild/instance-8/output-1/host/lib/gcc/sparc-buildroot-linux-uclibc/10.4.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /home/autobuild/autobuild/instance-8/output-1/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libssl.a(ssl_cert.o): in function `ssl_cert_free':
ssl_cert.c:(.text+0x53c): undefined reference to `__atomic_fetch_sub_4'

Fixes:
 - http://autobuild.buildroot.org/results/f606bb15bf4f88ba29ef0795413e13acc9cd0976



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>