freebsd: make check bench_bitcoin illegal instruction

OS: FreeBSD 14.2
Tag: Elements-23.2.4
Arch: x86_64

The bitcoind v23.2 bench_bitcoin runs fine.

```
% ./src/bench/bench_bitcoin

| ns/op | op/s | err% | total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
| 33,918,912.00 | 29.48 | 0.4% | 0.32 | `AddrManAdd`
| 41,379,012.00 | 24.17 | 0.2% | 0.46 | `AddrManAddThenGood`
| 143,318.71 | 6,977.46 | 0.2% | 0.01 | `AddrManGetAddr`
| 148.36 | 6,740,300.72 | 0.5% | 0.01 | `AddrManSelect`
| 349,355.33 | 2,862.42 | 0.2% | 0.01 | `AssembleBlock`

| ns/byte | byte/s | err% | total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
| 68.69 | 14,557,263.45 | 0.7% | 0.01 | `Base58CheckEncode`
| 15.00 | 66,656,073.03 | 0.3% | 0.01 | `Base58Decode`
| 50.84 | 19,670,034.41 | 0.3% | 0.01 | `Base58Encode`
| 7.09 | 141,086,434.00 | 0.1% | 0.01 | `Bech32Decode`
| 15.34 | 65,201,841.52 | 0.2% | 0.01 | `Bech32Encode`

| ns/op | op/s | err% | total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
| 134.03 | 7,461,269.48 | 0.8% | 0.01 | `BenchLockedPool`
| 28.87 | 34,637,621.14 | 0.0% | 0.01 | `BenchTimeDeprecated`
| 32.33 | 30,929,578.06 | 0.1% | 0.01 | `BenchTimeMillis`
| 32.31 | 30,953,487.11 | 0.2% | 0.01 | `BenchTimeMillisSys`
| 2.30 | 433,852,393.89 | 0.0% | 0.01 | `BenchTimeMock`
| 53,562,096.00 | 18.67 | 0.2% | 0.59 | `BlockToJsonVerbose`
| 33,862,387.00 | 29.53 | 0.3% | 0.38 | `BlockToJsonVerboseWrite`
| 677,365.50 | 1,476.31 | 0.1% | 0.01 | `BnBExhaustion`
Illegal instruction (core dumped)
```