[yocto] using the same download directory multiple times

[Jim Abernathy]

After reading the comments in the local.conf file about the download 
directory (DL_DIR), I experimented with creating it outside of the 
normal <build dir> directory used by "source oe-init-build-env <build 
dir>" command. After completing a build successfully, I examined the 
download directory and I'm trying to figure out what is in there besides 
the tarballs that were downloaded and the .done files for the matching 
tarball.  There also appear to be .done files that are not related to 
any tarball in the download directory.

What is the purpose of these files?

Apparently, all this works because I've recreated the same BSP in two 
different build directories with a common DL_DIR outside the build 
directory successfully.

Jim A