Workaround for forbidden artifact/crate names #58

Hi there!

Unfortunately, Cargo forbids a few names for packages or artifacts. See:

• https://github.com/rust-lang/cargo/blob/b42488270ed29d73445d6c81d303b6a7476f6bb1/src/cargo/util/toml/targets.rs#L247-L249
• https://github.com/rust-lang/cargo/blob/c8dce5bd07d093fa786a9c28fea9d6e5f465d00f/src/cargo/core/compiler/layout.rs#L74-L78
• and a few other places.

I noticed this because I wanted to have a build script build.rs. This leads to:

error: failed to parse manifest at `/home/lukas/.cargo/script-cache/file-build-5b0f8f572ede70cb/Cargo.toml`

Caused by:
  the binary target name `build` is forbidden
internal error: cargo failed with status 101

I am not sure why these names are forbidden, but it would be nice if they'd work with cargo-script. For example, one could check if the name of the script is on the blacklist and then just add -cargo-script or something. When executing a script, one usually doesn't care about the actual package and artifact name.