Support debug builds of terraform itself

[rbtcollins]

Quite likely an edge case, but I'm debugging a null pointer dereference in terraform (the shell itelf, not a particular provider). It would have been amazing to be able to say 'tfenv install --debug 1.6.1' and get a terraform binary that hasn't been stripped.

[kvendingoldo]

can you describe your case, pls? Now we're trying to support as many features of tfenv in https://github.com/tofuutils/tenv and would like to add this functionality too