bootstrap: implement a new utility file_lock

`file_lock` util provides `FileLock` type which is a wrapper around
`fs2` and `std::fs::File`. This is useful as `fs2` supports Solaris and has
fewer dependencies than `fd-lock`.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/src/lib.rs

@@ -51,6 +51,7 @@ pub use core::builder::PathSet;
 pub use core::config::flags::Subcommand;
 pub use core::config::Config;
 pub use utils::change_tracker::{find_recent_config_change_ids, CONFIG_CHANGE_HISTORY};
+pub use utils::file_lock::FileLock;
 
 const LLVM_TOOLS: &[&str] = &[
     "llvm-cov",      // used to generate coverage report

src/bootstrap/src/utils/file_lock.rs

@@ -0,0 +1,39 @@
+//! This module provides a `FileLock` type, serving as a cross-platform file-locking wrapper
+//! for `std::fs::File`, built on top of the `fs2` crate.
+//!
+//! Locks are automatically released by the `Drop` trait implementation when the `FileLock`
+//! instance goes out of scope.
+
+use std::{fs::File, io};
+
+use fs2::FileExt;
+
+use crate::t;
+
+pub struct FileLock(File);
+
+impl FileLock {
+    pub fn lock(&mut self) -> io::Result<&File> {
+        self.0.lock_exclusive()?;
+
+        Ok(&mut self.0)
+    }
+
+    pub fn try_lock(&mut self) -> io::Result<&File> {
+        self.0.try_lock_exclusive()?;
+
+        Ok(&mut self.0)
+    }
+}
+
+impl Drop for FileLock {
+    fn drop(&mut self) {
+        t!(self.0.unlock());
+    }
+}
+
+impl From<File> for FileLock {
+    fn from(file: File) -> Self {
+        Self(file)
+    }
+}

src/bootstrap/src/utils/mod.rs

@@ -8,6 +8,7 @@ pub(crate) mod change_tracker;
 pub(crate) mod channel;
 pub(crate) mod dylib;
 pub(crate) mod exec;
+pub(crate) mod file_lock;
 pub(crate) mod helpers;
 pub(crate) mod job;
 #[cfg(feature = "build-metrics")]