New review comment by DBLouis on void-packages repository

https://github.com/void-linux/void-packages/pull/30798#discussion_r632942831

Comment:
I originally tried it like that but it fails:

```
CMake Error:
  Running

   '/usr/bin/ninja' '-C' '/builddir/libphonenumber-8.12.23/cpp/build' '-t' 'recompact'

  failed with:

   ninja: error: build.ninja:1433: multiple rules generate ../src/phonenumbers/metadata.h [-w dupbuild=err]

CMake Generate step failed.  Build files cannot be regenerated correctly.
```