JIT compiled code crashes, crasher 2b5f

Crasher will be checked in shortly. Curious the minimized IR sample just fails with JIT miscompare:

```
package sample

fn __sample__main(x0: bits[50][9], x2: bits[5], x3: bits[18], x4: bits[51], x5: bits[30], x6: bits[58]) -> bits[51] {
sign_ext.8: bits[62] = sign_ext(x3, new_bit_count=62, id=8)
x7: bits[62] = literal(value=2305843009213693951, id=7, pos=0,6,20)
x8: bits[62] = add(sign_ext.8, x7, id=9, pos=0,7,32)
x9: bits[1] = dynamic_bit_slice(x7, x8, width=1, id=10, pos=0,8,21)
x23: bits[1] = not(x9, id=31, pos=0,20,18)
ret x36: bits[51] = zero_ext(x23, new_bit_count=51, id=57, pos=0,32,22)
}
```

```
$ xls/tools/eval_ir_main --input="[bits[50]:0x2_0c7a_c27b_22c4, bits[50]:0x1_ffff_ffff_ffff, bits[50]:0x2_f52c_0057_9850, bits[50]:0x1_ffff_ffff_ffff, bits[50]:0x3_ffff_ffff_ffff, bits[50]:0x1_5555_5555_5555, bits[50]:0x0, bits[50]:0x1_5555_5555_5555, bits[50]:0x3_ffff_ffff_ffff]; bits[5]:0x2; bits[18]:0x1; bits[51]:0x5_5555_5555_5555; bits[30]:0x3fff_ffff; bits[58]:0x132_9fff_d3ef_7cfb" minimized.ir --test_llvm_jit
bits[51]:0x1
bits[51]:0x7_ffff_ffff_ffff
F0405 14:35:09.209457 647321 eval_ir_main.cc:368] Check failed: ::absl::OkStatus() == (xls::RealMain(positional_arguments[0])) (OK vs. INVALID_ARGUMENT: Miscompare for input "[bits[50]:0x2_0c7a_c27b_22c4, bits[50]:0x1_ffff_ffff_ffff, bits[50]:0x2_f52c_0057_9850, bits[50]:0x1_ffff_ffff_ffff, bits[50]:0x3_ffff_ffff_ffff, bits[50]:0x1_5555_5555_5555, bits[50]:0x0, bits[50]:0x1_5555_5555_5555, bits[50]:0x3_ffff_ffff_ffff]; bits[5]:0x2; bits[18]:0x1; bits[51]:0x5_5555_5555_5555; bits[30]:0x3fff_ffff; bits[58]:0x132_9fff_d3ef_7cfb"
JIT: bits[51]:0x7_ffff_ffff_ffff
interpreter: bits[51]:0x1)
```