Log Message:
lang/ruby: fix build problem of Ruby 3.1 on NetBSD 8

Fix build problem of Ruby 3.1 on NetBSD 8 by disabling dtrace.

Ruby 3.1 dtrace(1) to modify compiled object files during build process.
But something wrong on NetBSD 8, includeing 8.2_STABLE.

For example, vm.o contains these symbols on NetBSD 9:

0000000000000000 A __dtrace_ruby___array__create
0000000000000000 A __dtrace_ruby___cmethod__entry
0000000000000000 A __dtrace_ruby___cmethod__return
0000000000000000 A __dtrace_ruby___hash__create
0000000000000000 A __dtrace_ruby___method__entry
0000000000000000 A __dtrace_ruby___method__return
0000000000000000 A __dtraceenabled_ruby___array__create
0000000000000000 A __dtraceenabled_ruby___cmethod__entry
0000000000000000 A __dtraceenabled_ruby___cmethod__return
0000000000000000 A __dtraceenabled_ruby___hash__create
0000000000000000 A __dtraceenabled_ruby___method__entry
0000000000000000 A __dtraceenabled_ruby___method__return

But on NetBSD 8:

0000000000000000 A __dtrace_ruby___array-create
0000000000000000 A __dtrace_ruby___cmethod-entry
0000000000000000 A __dtrace_ruby___cmethod-return
0000000000000000 A __dtrace_ruby___hash-create
0000000000000000 A __dtrace_ruby___method-entry
0000000000000000 A __dtrace_ruby___method-return
0000000000000000 A __dtraceenabled_ruby___array-create
0000000000000000 A __dtraceenabled_ruby___cmethod-entry
0000000000000000 A __dtraceenabled_ruby___cmethod-return
0000000000000000 A __dtraceenabled_ruby___hash-create
0000000000000000 A __dtraceenabled_ruby___method-entry
0000000000000000 A __dtraceenabled_ruby___method-return