seq: fails to parse hexadecimal floating-point arguments like 0x1p-1

While running `bash util/run-gnu-test.sh`, I encountered a bug where `seq` fails to handle hexadecimal arguments correctly. Specifically, the following command does not behave as expected:

```bash
$ cargo run -q seq 0x1p-1 2
seq: invalid hexadecimal argument: '0x1p-1'
$ seq 0x1p-1 2
0.5
1.5
```