The psych gem (version 5.1.1.1) fails to install on my machine, log contains:

conftest.c:3:10: fatal error: yaml.h: No such file or directory
    3 | #include <yaml.h>
      |          ^~~~~~~~
compilation terminated.
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: #include <yaml.h>
/* end */

As documented here, for example
https://github.com/sparklemotion/nokogiri#native-gems-faster-more-reliable-installation
there's a way to start from a pre-compiled native gem instead. I think most Bazel users should be using this to achieve reproducible builds.

(Of course, you could also imagine a cc_library to build the C extension, but then we're swapping out part of the bundle installer which is a bigger project)