MacOS, FreeBSD and Linux using GNU have it, but at least OpenBSD
does not (the non-compatible BSD equivalent jot(1) exists, though).
Counting up is easy enough to do in POSIX sh(1).
Looks like this after GNU make(1)'s escaping and produces the same
big-dynstr.c file:
```
cat main.c > big-dynstr.c
i=1; while [ $i -le 2000 ]; do echo "void f$i(void) { };"; i=$(($i + 1)); done >> big-dynstr.c
```
This is the last bit required to build and pass all tests on OpenBSD
without local patches/dependencies.
5f6cc74be8