[yocto] How to maintain a global DL_DIR?

[Patrick Doyle]

As I am playing with several different Yocto/OE projects, I thought it
would be nice to set up a global downloads directory.

Also, being a somewhat forgetful sort, I thought it would be nice if I
could set DL_DIR in my .bashrc and not have to remember to edit
conf/local.conf each time I follow the directions from a third party
site to set up their Yocto based distribution.

Can I do this?  If so, how?

Do I add DL_DIR to BB_ENV_WHITELIST?  Do I add it to
BB_ENV_EXTRAWHITE?  But I note that poky/scripts/oe-buildenv-internal
arbitrarily blasts its own values into BB_ENV_EXTRAWHITE, so setting
BB_ENV_EXTRAWHITE in my .bashrc won't work.

Perhaps I am misunderstanding the concept of the whitelist.  Perhaps I
should just ask for some help.

Help.

Can I maintain a single global download directory specified solely
through environment variables?  If so, how?

Thanks.

--wpd