uucore: disable default signal-handlers added by Rust

Fixes https://github.com/uutils/coreutils/issues/6759

Test procedure (verifies that a single SIGSEGV stops a program):
```
ecordonnier@lj8k2dq3:~/dev/coreutils$ ./target/release/coreutils sleep 100 &
[1] 4175464
ecordonnier@lj8k2dq3:~/dev/coreutils$ kill -11 $(pidof coreutils)
ecordonnier@lj8k2dq3:~/dev/coreutils$
[1]+  Segmentation fault      (core dumped) ./target/release/coreutils sleep 100
```

src/uucore/src/lib/lib.rs

@@ -4,6 +4,8 @@
 // file that was distributed with this source code.
 //! library ~ (core/bundler file)
 // #![deny(missing_docs)] //TODO: enable this
+//
+// spell-checker:ignore sigaction SIGBUS SIGSEGV
 
 // * feature-gated external crates (re-shared as public internal modules)
 #[cfg(feature = "libc")]
@@ -100,6 +102,12 @@ pub use crate::features::fsxattr;
 
 //## core functions
 
+#[cfg(unix)]
+use nix::errno::Errno;
+#[cfg(unix)]
+use nix::sys::signal::{
+    sigaction, SaFlags, SigAction, SigHandler::SigDfl, SigSet, Signal::SIGBUS, Signal::SIGSEGV,
+};
 use std::borrow::Cow;
 use std::ffi::OsStr;
 use std::ffi::OsString;
@@ -112,6 +120,25 @@ use std::sync::atomic::Ordering;
 
 use once_cell::sync::Lazy;
 
+/// Disables the custom signal handlers installed by Rust for stack-overflow handling. With those custom signal handlers processes ignore the first SIGBUS and SIGSEGV signal they receive.
+/// See <https://github.com/rust-lang/rust/blob/8ac1525e091d3db28e67adcbbd6db1e1deaa37fb/src/libstd/sys/unix/stack_overflow.rs#L71-L92> for details.
+#[cfg(unix)]
+pub fn disable_rust_signal_handlers() -> Result<(), Errno> {
+    unsafe {
+        sigaction(
+            SIGSEGV,
+            &SigAction::new(SigDfl, SaFlags::empty(), SigSet::all()),
+        )
+    }?;
+    unsafe {
+        sigaction(
+            SIGBUS,
+            &SigAction::new(SigDfl, SaFlags::empty(), SigSet::all()),
+        )
+    }?;
+    Ok(())
+}
+
 /// Execute utility code for `util`.
 ///
 /// This macro expands to a main function that invokes the `uumain` function in `util`

src/uucore_procs/src/lib.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 //
-// spell-checker:ignore backticks uuhelp
+// spell-checker:ignore backticks uuhelp SIGSEGV
 
 //! A collection of procedural macros for uutils.
 #![deny(missing_docs)]
@@ -25,6 +25,10 @@ pub fn main(_args: TokenStream, stream: TokenStream) -> TokenStream {
     let new = quote!(
         pub fn uumain(args: impl uucore::Args) -> i32 {
             #stream
+
+            // disable rust signal handlers (otherwise processes don't dump core after e.g. one SIGSEGV)
+            #[cfg(unix)]
+            uucore::disable_rust_signal_handlers().expect("Disabling rust signal handlers failed");
             let result = uumain(args);
             match result {
                 Ok(()) => uucore::error::get_exit_code(),