xous: include prelude to define c_int

[xobs]

Description

Include the prelude on Xous to fix the build in Rust libstd.

Sources

N/A

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

Extra

With the latest changes, libstd no longer builds:

   Compiling libc v0.2.170 (/opt/Xous/libc)
error[E0412]: cannot find type `c_int` in this scope
  --> /opt/Xous/libc/src/xous.rs:17:20
   |
17 | pub const INT_MIN: c_int = -2147483648;
   |                    ^^^^^ not found in this scope
   |
help: consider importing one of these type aliases
   |
5  + use crate::c_int;
   |
5  + use rustc_std_workspace_core::ffi::c_int;
   |

error[E0412]: cannot find type `c_int` in this scope
  --> /opt/Xous/libc/src/xous.rs:18:20
   |
18 | pub const INT_MAX: c_int = 2147483647;
   |                    ^^^^^ not found in this scope
   |
help: consider importing one of these type aliases
   |
5  + use crate::c_int;
   |
5  + use rustc_std_workspace_core::ffi::c_int;
   |

For more information about this error, try `rustc --explain E0412`.
error: could not compile `libc` (lib) due to 2 previous errors

[rustbot]

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[xobs]

An example of a build failure in CI can be found at https://github.com/betrusted-io/rust-nightly/actions/runs/13699992351/job/38311095367

[tgross35]

Sorry about that, thanks for sending a fix.

@rustbot label +stable-nominated

[tgross35]

Sorry I didn't check the branch, could you send this against main instead? I cherry pick to 0.2.

[xobs]

Sure. PR open at #4304