Remove Target Directories Should Never be Mounted at `/cross/target`

[Alexhuszagh]

Since our remote builds us data volumes, which are shared between multiple images, we should always mount the target directory at the full path in the data volume. Otherwise, we could have mixing between multiple different packages, which would cause nonsensical builds. This wasn't an issue when remote data volumes were package-specific, however, not that they're universal for a given toolchain, this needs to be reworked.