Remove direct libc dependency from orchestrator-process and environmentd (#35929)

## Summary
- **orchestrator-process**: Replace `libc::{SIGABRT, SIGBUS, SIGILL,
SIGSEGV, SIGTRAP}` with `nix::sys::signal::Signal` variants (nix already
a dependency)
- **environmentd**: Replace `libc::raise` with `nix::sys::signal::raise`
and `libc::c_int` with `std::ffi::c_int`

Both crates already depend on `nix` which re-exports these via safe
APIs. No new dependencies added.

## Test plan
- [x] `cargo check -p mz-orchestrator-process -p mz-environmentd` passes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Jason Hernandez <7144515+jasonhernandez@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jasonhernandez

Cargo.lock

@@ -36,7 +36,6 @@ include_dir.workspace = true
 ipnet.workspace = true
 itertools.workspace = true
 jsonwebtoken.workspace = true
-libc.workspace = true
 maplit.workspace = true
 mime.workspace = true
 mz-alloc = { path = "../alloc" }

src/environmentd/Cargo.toml

@@ -10,7 +10,6 @@
 //! System support functions.
 
 use anyhow::Context;
-use nix::errno;
 use nix::sys::signal;
 use tracing::trace;
 
@@ -131,7 +130,7 @@ pub fn enable_termination_signal_cleanup() -> Result<(), anyhow::Error> {
 }
 
 unsafe extern "C" {
-    fn __llvm_profile_write_file() -> libc::c_int;
+    fn __llvm_profile_write_file() -> std::ffi::c_int;
 }
 
 extern "C" fn handle_sigusr2_signal(_: i32) {
@@ -149,9 +148,6 @@ extern "C" fn handle_termination_signal(signum: i32) {
     unsafe { signal::sigaction(signum.try_into().unwrap(), &action) }
         .unwrap_or_else(|_| panic!("failed to uninstall handler for {}", signum));
 
-    let ret = unsafe { libc::raise(signum) };
-    if ret == -1 {
-        let errno = errno::Errno::from_raw(errno::Errno::last_raw());
-        panic!("failed to re-raise signal {}: {}", signum, errno);
-    }
+    signal::raise(signum.try_into().unwrap())
+        .unwrap_or_else(|e| panic!("failed to re-raise signal {}: {}", signum, e));
 }

src/environmentd/src/environmentd/sys.rs

@@ -17,7 +17,6 @@ chrono.workspace = true
 futures.workspace = true
 hex.workspace = true
 itertools.workspace = true
-libc.workspace = true
 maplit.workspace = true
 mz-orchestrator = { path = "../orchestrator", default-features = false }
 mz-ore = { path = "../ore", default-features = false, features = ["async", "network"] }

src/orchestrator-process/Cargo.toml

@@ -30,7 +30,6 @@ use chrono::{DateTime, Utc};
 use futures::StreamExt;
 use futures::stream::{BoxStream, FuturesUnordered};
 use itertools::Itertools;
-use libc::{SIGABRT, SIGBUS, SIGILL, SIGSEGV, SIGTRAP};
 use maplit::btreemap;
 use mz_orchestrator::scheduling_config::ServiceSchedulingConfig;
 use mz_orchestrator::{
@@ -43,6 +42,7 @@ use mz_ore::error::ErrorExt;
 use mz_ore::netio::UnixSocketAddr;
 use mz_ore::result::ResultExt;
 use mz_ore::task::AbortOnDropHandle;
+use nix::sys::signal::Signal;
 use scopeguard::defer;
 use serde::Serialize;
 use sha1::{Digest, Sha1};
@@ -1037,10 +1037,16 @@ fn did_process_crash(status: ExitStatus) -> bool {
     // Likely not exhaustive. Feel free to add additional tests for other
     // indications of a crashed child process, as those conditions are
     // discovered.
-    matches!(
-        status.signal(),
-        Some(SIGABRT | SIGBUS | SIGSEGV | SIGTRAP | SIGILL)
-    )
+    status.signal().is_some_and(|s| {
+        matches!(
+            Signal::try_from(s),
+            Ok(Signal::SIGABRT
+                | Signal::SIGBUS
+                | Signal::SIGSEGV
+                | Signal::SIGTRAP
+                | Signal::SIGILL)
+        )
+    })
 }
 
 async fn write_pid_file(pid_file: &Path, pid: Pid) -> Result<(), anyhow::Error> {