The attached patch adds support for the --with-dependency-source 
common build option. It can be used to specify the sources of 
dependencies of specified packages. With this step, we can close #42155. 
This is also a step in closing #43061.

Note that I suggested making a new 
--with-dependency-source=package=source build option in response to 
#42155 and nobody responded with an objection. So I am sending this 
patch with the assumption that there are no objections to this new build 
option, and that if a member of the community wants to completely 
replace the behavior of --with-source with the behavior of the new 
option, that person can do the work required to not break 
--with-source=source.

-Jesse