fix: use write_all() instead of write() to write the header, since write() is not guaranteed to write the entire buffer

Author: nickysn

runtime_tracing/src/capnptrace.rs

@@ -309,7 +309,7 @@ pub fn write_trace(q: &Vec<crate::TraceLowLevelEvent>, output: &mut impl std::io
         }
     }
 
-    output.write(HEADER)?;
+    output.write_all(HEADER)?;
 
     serialize_packed::write_message(output, &message)
 }