- `cargo rustc` is starting out based on `cargo build`

- The new field is a list with arguments to compile the target with.
- There should only be one target that gets compiled with these arguments

…tions.

- The new tests verifies that the extra arguments gets appended to the command. One is for lib and one is for main
- Currently the arguments gets passed on to *every* target that gets built, so the tests only contain one file each

- This field will be set by the `cargo rustc` command, only if one target is being compiled
- The field can not be read from the Cargo.toml

…e that's being compiled instead.

- An error will be returned if the length of `targets` is not 1
- The profile of `targets` gets cloned in order to append the extra arguments.
- The new test verifies that the build fails due to both `lib` and `main` being compiled

… a dependency.

- The test verifies that the trailing arguments only gets passed to the binary being built

…helper functions

- `build_with_args_to_one_of_multiple_binaries`, verify that only one bin gets built
- `fails_with_args_to_all_binaries`
- `build_with_args_to_one_of_multiple_tests`, same behavious as for the binaries
- `build_foo_with_bar_dependency`, verify that bar dependency gets built and only foo gets compiled with args
- `build_only_bar_dependency`, build the bar package, that foo depends, on with the extra args

- Dereference arguments before matching
- use square brackets for vec! macro