Dump backtrace if a core dump is called just "core" (#9125)

I hope this lets us capture backtraces in CI. At least it makes it
work on my laptop, which is valuable even if we need to do more for
CI.

See issue #2800.

compute_tools/src/compute.rs

@@ -1123,6 +1123,9 @@ impl ComputeNode {
     //
     // Use that as a default location and pattern, except macos where core dumps are written
     // to /cores/ directory by default.
+    //
+    // With default Linux settings, the core dump file is called just "core", so check for
+    // that too.
     pub fn check_for_core_dumps(&self) -> Result<()> {
         let core_dump_dir = match std::env::consts::OS {
             "macos" => Path::new("/cores/"),
@@ -1134,8 +1137,17 @@ impl ComputeNode {
         let files = fs::read_dir(core_dump_dir)?;
         let cores = files.filter_map(|entry| {
             let entry = entry.ok()?;
-            let _ = entry.file_name().to_str()?.strip_prefix("core.")?;
-            Some(entry.path())
+
+            let is_core_dump = match entry.file_name().to_str()? {
+                n if n.starts_with("core.") => true,
+                "core" => true,
+                _ => false,
+            };
+            if is_core_dump {
+                Some(entry.path())
+            } else {
+                None
+            }
         });
 
         // Print backtrace for each core dump