Fixes some tests by referencing the test binary.

Index: tests/util/server/src/lib.rs
--- tests/util/server/src/lib.rs.orig
+++ tests/util/server/src/lib.rs
@@ -229,8 +229,8 @@ pub fn std_file_url() -> String {
 }
 
 pub fn target_dir() -> PathRef {
-  let current_exe = std::env::current_exe().unwrap();
-  let target_dir = current_exe.parent().unwrap().parent().unwrap();
+  let current_exe = PathBuf::from("${WRKSRC}/target/release/deno");
+  let target_dir = current_exe.parent().unwrap();
   PathRef::new(target_dir)
 }
 
