fix(valgrind): allow file caps on the runner's own executable

The memory executor grants file capabilities to the runner's executable,
and valgrind refuses to run an executable that carries them. A simulation
run of an exec target then failed with "Permission denied" (exit code
126) as soon as the executable had been granted them, since exec-harness
runs through it.

Pass --allow-file-caps with the runner's executable path, so valgrind
runs it without the capabilities, which its internal subcommands do not
need. This option requires a valgrind-codspeed build that supports it.

Refs COD-3722
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: lvaroqui

src/executor/valgrind/measure.rs

@@ -63,6 +63,13 @@ fn get_valgrind_args(tool: &SimulationTool, config: &ExecutorConfig) -> Vec<Stri
         children_skip_patterns.join(",")
     ));
 
+    // Internal subcommands run through the runner's own executable, which may
+    // carry file capabilities that valgrind refuses to run by default. They
+    // do not need those capabilities.
+    if let Ok(self_exe) = crate::cli::self_exe() {
+        args.push(format!("--allow-file-caps={}", self_exe.display()));
+    }
+
     if config.fair_sched {
         args.push("--fair-sched=yes".to_string());
     }