Fix issue when two -dev packages provides same pkg-config wil but with
different versions. For example libressl-dev and openssl-dev both ships
libssl.pc and libcrypto.pc, which resulted in automatic provides of
pc:libssl and pc:libcrypto.
apk would end up picking libressl-dev over openssl-dev for packages that
had automatic pc:libssl depends (for example libssl2-dev), when
openssl-dev was the one that was used during build.
To fix this we add support for a pcprefix so we can set
pcprefix="libressl:" in libressl APKBUILD which makes libressl-dev
provide pc:libressl:libssl. This is similar to what we do with
sonameprefix.
We do not yet automatically detect when the prefixed variant should be
used so for now we will have to explicitly add libressl-dev.
ref #9959
376ccc5bd6