Move libc from hyperlight-guest-bin to hyperlight-libc

[jprendes]

Fixes #1398
Requires a new release of cargo-hyperlight that includes hyperlight-dev/cargo-hyperlight#50

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Moves the picolibc/libc integration out of hyperlight-guest-bin into a new hyperlight-libc crate, updating repository references accordingly.

Changes:

• Adds a new hyperlight-libc workspace crate intended to provide picolibc + generated Rust bindings.
• Updates hyperlight-guest-bin to depend on and re-export hyperlight-libc behind the libc feature.
• Updates docs, scripts, and submodule paths to reference src/hyperlight_libc/third_party/picolibc.

Reviewed changes

Copilot reviewed 13 out of 21 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/tests/c_guests/c_simpleguest/main.c	Updates comment to reflect the new picolibc location.
src/hyperlight_libc/src/lib.rs	Introduces the new hyperlight-libc crate API surface (bindings include).
src/hyperlight_libc/Cargo.toml	Defines the new crate and its build dependencies for compiling/binding generation.
src/hyperlight_libc/.cargo/config.toml	Sets a default target for building the new crate.
src/hyperlight_guest_bin/src/libc.rs	Refactors guest libc stubs to consume types/constants from generated bindings.
src/hyperlight_guest_bin/src/lib.rs	Switches guest-bin to re-export hyperlight-libc and renames the local module.
src/hyperlight_guest_bin/build.rs	Modifies build logic to build libc and generate bindings (currently still located in guest-bin).
src/hyperlight_guest_bin/Cargo.toml	Removes links and wires the libc feature to depend on hyperlight-libc.
docs/picolibc.md	Updates documentation paths to the new picolibc location.
c.just	Updates C include paths to point at the new picolibc/include locations.
NOTICE.txt	Updates license notice path to the new picolibc submodule location.
Cargo.toml	Adds hyperlight-libc to the workspace and workspace dependencies.
.gitmodules	Moves the picolibc submodule path from guest-bin to hyperlight-libc.

[andreiltd]

I think this is great! One thing that would be nice is if we had README file in the new crate that documents what system interface or stubs the embedder needs to implement with the reference to the implementation in the guest_bin.

I think this is partially described in the picolibc.md file as well.

The picolibc documents it here: https://github.com/hyperlight-dev/picolibc-bsd/blob/main/doc/os.md