Log Message:
devel/bison: do not suggest nls option on Darwin

The previous commit message included the following comment:

    TODO: avoid suggesting nls on macOS/x86_64 versions where bison
    will crash.

Additionally, options.mk contains a comment suggesting the crash only
occurs for versions less than or equal to approximately 11.6.  This
commit adds conditionals to options.mk to suggest the nls option only
when crashes are not expected.