Add 'build_script_exec_properties' to 'crate.annotation'

[alloveras]

Intent

To allow specifying exec_properties via crate.annotation.

Problem

The current implementation allows tweaking a few of the attributes that get generated for the cargo_build_script rule, but, unfortunately, not the exec_properties.

My current use case for which I want to be able to specify exec_properties is a semi-large build script that gets performance benefits from running on machines with multiple CPUs. If you are not using remote execution, it essentially boils down to whatever hardware you have available locally. However, if RBE is available, being able to set exec_properties = {"Pool": "<pool-with-powerful-hardware>"} allows you to specifically steer these build actions to the machines that you want to run them on.

Solution

To extend the current cargo-bazel code along with the relevant Starlark code to make it possible to specify exec_properties for the generated cargo_build_script rules.

[alloveras]

I think I have to run some magic command(s) to update the lockfile checksums, but I couldn't find the correct incantation anywhere 😢 Otherwise, CI fails complaining about the checksum mismatch.

I tried CARGO_BAZEL_REPIN=1 bazel test //... but that didnt' seem to help, unfortunately. Will try ./util/repin_all.sh and report back.

Edit: It seems like running ./util/repin_all.sh did the trick 🎉

[illicitonion]

Looks reasonable, thanks!