Improve FreeBSD support (#33162)

This PR contains a set of changes for improving FreeBSD support (#15309,
#29550) and is a kind of follow up to the PR #20480 which added an
initial support for FreeBSD.

A summary of changes is as follows:
- Add some more freebsd conditionals which seem missing in the previous
PR.
- Implement `anonymous_fd()` and `current_path()` functions for FreeBSD.
- Improve detection of FreeBSD in telemetry and GPU detection.
- Temporarily disable LiveKit/WebRTC support to make build succeed.
- Remove support for flatpak since it is Linux-only packaging format.

Adding `RUSTFLAGS="-C link-dead-code"` does not seem necessary anymore.
It builds fine without the flag.

Known issues:
- Integrated terminal is painfully laggy and virtually unusable in my
environment. This might be specific to my setup.
- I cannot input Japanese using IME. When I type characters, they appear
on the screen. But when I hit return key, they disappears. Seems the
same issue as #15409.

My environment is MATE desktop on X11 on FreeBSD 14.2 on Intel Core
i5-7260U integrated graphics.

P.S. For those who might be interested, a work-in-progress FreeBSD port
and binary packages are available at
https://github.com/tagattie/FreeBSD-Zed

Release Notes:

- N/A

---------

Co-authored-by: Peter Tripp <peter@zed.dev>

crates/cli/src/main.rs

@@ -134,7 +134,7 @@ fn main() -> Result<()> {
     util::prevent_root_execution();
 
     // Exit flatpak sandbox if needed
-    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
+    #[cfg(target_os = "linux")]
     {
         flatpak::try_restart_to_host();
         flatpak::ld_extra_libs();
@@ -158,7 +158,7 @@ fn main() -> Result<()> {
         paths::set_custom_data_dir(dir);
     }
 
-    #[cfg(any(target_os = "linux", target_os = "freebsd"))]
+    #[cfg(target_os = "linux")]
     let args = flatpak::set_bin_if_no_escape(args);
 
     let app = Detect::detect(args.zed.as_deref()).context("Bundle detection")?;
@@ -374,7 +374,7 @@ fn anonymous_fd(path: &str) -> Option<fs::File> {
         let file = unsafe { fs::File::from_raw_fd(fd) };
         return Some(file);
     }
-    #[cfg(target_os = "macos")]
+    #[cfg(any(target_os = "macos", target_os = "freebsd"))]
     {
         use std::os::{
             fd::{self, FromRawFd},
@@ -392,7 +392,7 @@ fn anonymous_fd(path: &str) -> Option<fs::File> {
         let file = unsafe { fs::File::from_raw_fd(fd) };
         return Some(file);
     }
-    #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+    #[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "freebsd")))]
     {
         _ = path;
         // not implemented for bsd, windows. Could be, but isn't yet
@@ -537,7 +537,7 @@ mod linux {
     }
 }
 
-#[cfg(any(target_os = "linux", target_os = "freebsd"))]
+#[cfg(target_os = "linux")]
 mod flatpak {
     use std::ffi::OsString;
     use std::path::PathBuf;