Add a package cache

[nicolamori]

Is your feature request related to a problem? Please describe.

Currently, the concept of build and cache folder is the same: a single folder is used to build the package and to store it. Since I use /tmp for building (both for speed and for preserving my SSD) I end up with package files in /tmp, which are wiped away at shutdown. This means that when uninstalling a package I have to rebuild it for reinstalling instead of reusing the already built package file.

Describe the solution you'd like

Add a package cache folder, eventually different from the build folder, where the built packages are automatically transferred after build.

[Morganamilo]

Set PKGDEST

[nicolamori]

Thank you @Morganamilo.