New review comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/27608#discussion_r578168482

Comment:
Given that the file looks like

```
prefix=/usr
libdir=/usr//usr/lib
includedir=/usr/include
CXX=/usr/lib/ccache/bin/g++ 
CC=/usr/lib/ccache/bin/cc 
DEPENDENCIES=/usr/lib/libtinyxml.so

Name: kodiplatform
Description: Kodi add-on platform support library 18.0
Version: 18.0
Libs: -L -l:kodiplatform -ltinyxml
Cflags: -fstack-clash-protection -D_FORTIFY_SOURCE=2 -mtune=generic -O2 -pipe   -g -std=c++11 -fPIC
```

for native builds, the issue is that `/usr//usr/lib` appears at all. I would attribute it to `-DCMAKE_INSTALL_LIBDIR=/usr/lib`.