[RFC][Rust Planner] Reduce image size by using glibc, and copying built binary

[savil]

Summary

Reduce image size by

1. Replace gcc with glibc in the Runtime image.

   • gcc is needed in the DevPackages for the Build Stage. Replacing it with glibc doesn't work because glibc nix pkg is not available on mac OS (linux only). We want universal packages (defined as linux and mac, lol) since we share DevPackages with devbox shell.

2. Copy just the specific built binary to the Runtime image.

How was it tested?

Using the basic testdata/rust/rust-stable-hello-world project:

• before, size of image = 320MB
• after, size of image = 64MB

[savil]

Current dependencies on/for this PR:

• main
  • PR [RFC][Rust Planner] Reduce image size by using glibc, and copying built binary #132 👈

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[savil]

Tests are failing due to this getFileNames logic in devbox_test, which I don't quite understand the motivation for: https://github.com/jetpack-io/devbox/blame/26e7e8297aa5e4e31f9926328d98fbf62fc375a2/devbox_test.go#L58-L64

[savil]

@loreto @gcurtis PTAL. Updated to use glibc, as per our discussion IRL.

[savil]

verified with @LucilleH that it makes sense to drop getFileNames for StartStage.

Because:

1. The motivation to introduce getFileNames was to normalize the filepaths used. The filepaths would differ based on which directory the go test command is invoked from.
2. This doesn't apply to StartStage, since the InputFiles are relative to the BuildStage's container. And not relative to the local laptop/CICD invoking go test.

[loreto]

LGTM