Fix #45345.
Fix #45345.

Re-implement

```bash
CFG_LIBDIR_RELATIVE=`echo ${CFG_LIBDIR} | cut -c$((${#CFG_PREFIX}+${CAT_INC}))-`
```

from old `configure` script.

graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust