support multiple compilation units for foundry (2)

[montyly]

Something fishy is going on with mypy on #334. I am trying to debug it

[montyly]

Turned out, this was the issue:

crytic-compile/crytic_compile/platform/hardhat.py

Line 172 in 6e2f404

hardhat_working_dir = str(Path(self._target, detected_paths["root"]))

A change made in dev, but this branch was not up to date with dev :)

I also changed the message here:

crytic-compile/crytic_compile/platform/hardhat.py

Line 52 in 6e2f404

txt = f"`compile` failed. Can you run it?\n{build_directory} is empty"

. Previously it would show "hardhat compile failed for foundry, not it only mentions the that the compile failed.

@0xalpharush / @bohendo : could one of you do a review, to make sure I did not mess up with #334

[0xalpharush]

Tested on 3 repos and seems to not have broken anything