chore: canonical exe path before validating.

We validate that the dpd path lives at the expected location on start. However,
this check can throw a false positive if we point to the exe via a symlink.
This patch canonicalizes the exe path before validating so that we validate the
real exe path, which may differ from env::current_exe().

Author: jmcarp

asic/src/tofino_common/mod.rs

@@ -4,6 +4,7 @@
 //
 // Copyright 2025 Oxide Computer Company
 
+use std::fs;
 use std::collections::HashMap;
 use std::ffi::OsStr;
 use std::path::PathBuf;
@@ -240,6 +241,10 @@ fn infer_p4_dir() -> AsicResult<String> {
     let mut exe_path = std::env::current_exe().map_err(|e| {
         AsicError::P4Missing(format!("looking up dpd path: {e:?}"))
     })?;
+    // Canonicalize the path in case we're using a symlinked exe.
+    exe_path = fs::canonicalize(exe_path).map_err(|e| {
+        AsicError::P4Missing(format!("canonicalizing dpd path: {e:?}"))
+    })?;
 
     // Pop off the trailing "dpd":
     exe_path = expect_name(exe_path, "dpd")?;