feat: upgrade toolchain to nightly-2025-12-12

[AsakuraMizu]

Related:

• https://github.com/orgs/Starry-OS/discussions/22
• feat: upgrade toolchain to nightly-2025-12-12 arceos-org/arceos#313

[Copilot]

Pull request overview

This PR upgrades the Rust toolchain from nightly-2025-05-20 to nightly-2025-12-12, updating code to comply with newer compiler requirements around explicit lifetime annotations and modern API usage.

Key Changes:

• Toolchain updated to nightly-2025-12-12
• Added explicit lifetime parameters ('_) to Cow return types across multiple file implementations
• Replaced deprecated modulo checks with is_multiple_of() method
• Updated PartialOrd implementation to use Ord::cmp() method

Reviewed changes

Copilot reviewed 17 out of 18 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
rust-toolchain.toml	Updates toolchain channel to nightly-2025-12-12
core/src/vfs/file.rs	Adds explicit lifetime annotations to Cow<[u8]> return types
core/src/time.rs	Refactors PartialOrd implementation to delegate to Ord::cmp()
core/src/futex.rs	Adds explicit lifetime annotations to FutexGuard return types
arceos	Updates subproject commit hash
api/src/syscall/task/thread.rs	Moves unused import to inline usage and adds architecture-specific conditional compilation
api/src/syscall/mm/mmap.rs	Replaces modulo check with is_multiple_of() method
api/src/lib.rs	Removes maybe_uninit_slice feature flag
api/src/syscall/fs/io.rs	Adds explicit lifetime annotation to path() return type
api/src/file/signalfd.rs	Adds explicit lifetime annotation to path() return type
api/src/file/pipe.rs	Adds explicit lifetime annotation to path() return type
api/src/file/pidfd.rs	Adds explicit lifetime annotation to path() return type
api/src/file/net.rs	Adds explicit lifetime annotation to path() return type
api/src/file/mod.rs	Adds explicit lifetime annotation to trait method path() return type
api/src/file/fs.rs	Adds explicit lifetime annotation to path() return type
api/src/file/event.rs	Adds explicit lifetime annotation to path() return type
api/src/file/epoll.rs	Adds explicit lifetime annotation to path() return type

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