dub build --compiler=ldmd2 overwrites files in ~/.dub written by dub build

[timotheecour]

can dub build --compiler=ldmd2 coexist with dub build? it seems like it creates conflicts as it overwrites the generated files in ~/.dub
shouldn't dub cache the generated files in directories that depend on cmd line options (eg dmd vs ldmd2)?

EDIT: dub build --compiler=ldmd2 --cache=local still seems to affect ~/.dub

in dub/source/dub/dub.d I see HOME is hardcoded:
m_dirs.userSettings = NativePath(environment.get("HOME")) ~ ".dub/";
a temporary fix is to use:
HOME=other_dir dub build --compiler=ldmd2
however this is hacky and not a good idea to override HOME; could we use a different environment variable for this? eg: DUB_HOME which defaults to HOME?

or preferably a dub option: dub build --dub_home=...

NOTE: it's also being used in dub describe and probably other commands