[OE-core] [PATCH] package.bbclass: Include dbgsrc for static libs

[Ola x Nilsson]

You were right, I needed to check if it was a proper file.

I stumbled into another issue, that golang .a files can not be read by
dwarfsrcfiles.  I'm not familiar with go, so I don't really know what
to do about it.  This patch is still an improvement in my book, even
if it cannot handle go archives.

New in v2:
 * do not process symbolic links
 * do not process golang .a files