`dslx_jit_wrapper` needs to anonymous namespace ir_text to avoid ODR violations?

[cdleary]

Noticed the source files all have ir_text[] in the xls namespace -- even though it's constexpr char char ir_text[] still can cause ODR violations I presume (and these I imagine would be confusing since we'd JIT the wrong thing)?

[meheff]

Related issue: https://github.com/google/xls/issues/733

I'm guessing this issue can be fixed by putting ir_text into an anonymous namespace.