(minor) syntactic sugar to use lighttpd.conf include_shell to set var.rootroot

```
# Be nice to not have to use an absolute path here.
var.rootroot="/home/stephen/code/openssl/esnistuff"
```

https://github.com/sftcd/openssl/blob/512c18169eb668db2b4b4b8c43e8d8ed91151bb2/esnistuff/lighttpdmin.conf#L4

This might do what you want for testing (current working directory).
`include_shell "printf var.rootroot=\\"$PWD\\""`
