Add initial FreeBSD support (#20480)

This PR adds initial support for FreeBSD
(https://github.com/zed-industries/zed/issues/15309). While there is
still work left to be done, it seems to be usable. As discussed by
@syobocat (https://github.com/zed-industries/zed/discussions/10247), the
changes were just adding ```target_os = "freebsd"``` to wherever it
checks if the OS is Linux.


![image](https://github.com/user-attachments/assets/80ea5b29-047f-4cbd-8263-42e5fa6c94b7)

Needs to be build with ```RUSTFLAGS="-C link-dead-code"```

Known Issues:
- There's an issue in ```crates/project/src/environment.rs``` where a
command fails because ```/bin/sh``` on FreeBSD doesn't support the
```-l``` option.

![image](https://github.com/user-attachments/assets/c3c38633-160f-4f47-8840-e3da67f6ebc8)
- The file/folder choosers provided by the ```ashpd``` crate don't work
on FreeBSD (at least with KDE). This isn't that bad since a fallback
dialog is used.

![image](https://github.com/user-attachments/assets/29373006-1eb9-4ed0-bd52-2d0047fab418)
 - Moving to trash won't work.
- Numerous tests fail (when running on FreeBSD). While I haven't looked
into this much, it appears that the corresponding features seem to work
fine.

Release Notes:

- Added initial support for FreeBSD

crates/fs/src/fs.rs

@@ -1,15 +1,15 @@
 #[cfg(target_os = "macos")]
 mod mac_watcher;
 
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
 pub mod linux_watcher;
 
 use anyhow::{anyhow, Result};
 use git::GitHostingProviderRegistry;
 
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
 use ashpd::desktop::trash;
-#[cfg(target_os = "linux")]
+#[cfg(any(target_os = "linux", target_os = "freebsd"))]
 use std::fs::File;
 #[cfg(unix)]
 use std::os::fd::AsFd;
@@ -217,7 +217,7 @@ impl FileHandle for std::fs::File {
         Ok(path)
     }
 
-    #[cfg(target_os = "linux")]
+    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     fn current_path(&self, _: &Arc<dyn Fs>) -> Result<PathBuf> {
         let fd = self.as_fd();
         let fd_path = format!("/proc/self/fd/{}", fd.as_raw_fd());
@@ -391,7 +391,7 @@ impl Fs for RealFs {
         Ok(())
     }
 
-    #[cfg(target_os = "linux")]
+    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     async fn trash_file(&self, path: &Path, _options: RemoveOptions) -> Result<()> {
         let file = File::open(path)?;
         match trash::trash_file(&file.as_fd()).await {
@@ -423,7 +423,7 @@ impl Fs for RealFs {
         self.trash_file(path, options).await
     }
 
-    #[cfg(target_os = "linux")]
+    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     async fn trash_dir(&self, path: &Path, options: RemoveOptions) -> Result<()> {
         self.trash_file(path, options).await
     }
@@ -468,7 +468,7 @@ impl Fs for RealFs {
 
     async fn atomic_write(&self, path: PathBuf, data: String) -> Result<()> {
         smol::unblock(move || {
-            let mut tmp_file = if cfg!(target_os = "linux") {
+            let mut tmp_file = if cfg!(any(target_os = "linux", target_os = "freebsd")) {
                 // Use the directory of the destination as temp dir to avoid
                 // invalid cross-device link error, and XDG_CACHE_DIR for fallback.
                 // See https://github.com/zed-industries/zed/pull/8437 for more details.
@@ -634,7 +634,7 @@ impl Fs for RealFs {
         )
     }
 
-    #[cfg(target_os = "linux")]
+    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
     async fn watch(
         &self,
         path: &Path,
@@ -781,7 +781,7 @@ impl Fs for RealFs {
     }
 }
 
-#[cfg(not(target_os = "linux"))]
+#[cfg(not(any(target_os = "linux", target_os = "freebsd")))]
 impl Watcher for RealWatcher {
     fn add(&self, _: &Path) -> Result<()> {
         Ok(())

crates/fs/src/linux_watcher.rs

@@ -85,7 +85,10 @@ impl Watcher for LinuxWatcher {
 
 pub struct GlobalWatcher {
     // two mutexes because calling inotify.add triggers an inotify.event, which needs watchers.
+    #[cfg(target_os = "linux")]
     pub(super) inotify: Mutex<notify::INotifyWatcher>,
+    #[cfg(target_os = "freebsd")]
+    pub(super) inotify: Mutex<notify::KqueueWatcher>,
     pub(super) watchers: Mutex<Vec<Box<dyn Fn(&notify::Event) + Send + Sync>>>,
 }