luajit-dev's pkgconfig is not taken into account by apk
On edge or 3.9.2, I’ve installed `luajit-dev`.
Running `apk info —installed "pc:luajit` returns nothing even though
`/usr/lib/pkgconfig/luajit.pc` is installed by the package.
(from redmine: issue id 10089, created on 2019-03-11)