objdump may be prefixed on cross-compilation, read the path from $OBJDUMP instead

diff --git a/tests/symbols.rs b/tests/symbols.rs
index 9375619..5f161fc 100644
--- a/tests/symbols.rs
+++ b/tests/symbols.rs
@@ -27,7 +27,10 @@ fn symbols() -> anyhow::Result<()> {
         }
     };
 
-    let cmd = Command::new("objdump")
+    let cmd = Command::new("bash")
+        .arg("-c")
+        .arg(r#"exec "$OBJDUMP" "$@""#)
+        .arg("--")
         .arg("-T")
         .arg(lib)
         .unwrap();