New review comment by classabbyamp on void-packages repository

https://github.com/void-linux/void-packages/pull/39984#discussion_r997580278

Comment:
```suggestion

post_patch() {
	vsed -e 's,./date.pl; ,,' -i Makefile
	# taken from date.pl, changed for reproducibility
	vsed -e 's/You are using an executable made on.*/You are using an executable made on '"$(date --utc --date @$SOURCE_DATE_EPOCH +%Y-%m-%d)"'\\n");/g' \
		-i ccx_$version.c -i CalculiXstep.c
	vsed -e 's/COMPILETIME.*/COMPILETIME       '"$(date --utc --date @$SOURCE_DATE_EPOCH +%Y-%m-%d)"'\\n",p1);/g' \
		-i frd.c
}

```
instead of `date.pl` (which is broken, there's an incorrect filename), we can do the same thing manually, and at the time use a more reproducible method of getting the date.