package/ruby: links with atomic if needed

Build fails since bump to version 3.0.0 in commit
af5226f2 because ruby needs atomic
operation support since
https://github.com/ruby/ruby/commit/6ed6b85ece8733518a7da0c3ec714f20d1102bf5

Fixes:
 - http://autobuild.buildroot.org/results/84ee5f4688be994a5440c3a61bddabee72ca3b3c



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