Add 'it links' tests

[v-thakkar]

Add tests for the minimal embedded program which can link with bunch of compiler options like [but not limited to] incremental, opt-level etc. We aim to add these tests no later than August 19, 2018. [Rust 1.29 ship date: September 13, 2018].

It would be good to sort of make a list of bunch of compiler options we aim to link with the program and then prioritize them. The more tests are useful but we need to keep the deadline in mind as well.

[sekineh]

It will need to run cargo on some crate successfully. At the same time, #2 is also satisfied.

[sekineh]

Do the same as #2, but use binary crate this time.

[v-thakkar]

Just linking Japric's comment here for the reference: rust-embedded/wg#52 (comment)