clang-tidy: Enable performance-unnecessary-value-param check

This check flags value parameter declarations of expensive to copy
types that are copied for each invocation but it would suffice to
pass them by const reference.

Change-Id: I631deda63fcbb74362313c9596bf7e72933b0d0c
Signed-off-by: Pavithra Barithaya <pavithrabarithaya07@gmail.com>
diff --git a/test/utest.cpp b/test/utest.cpp
index 8e3edd3..5d3d10d 100644
--- a/test/utest.cpp
+++ b/test/utest.cpp
@@ -354,7 +354,7 @@
 class FileTest : public testing::Test
 {
   protected:
-    std::string readFile(fs::path path)
+    std::string readFile(const fs::path& path)
     {
         std::ifstream f(path, std::ios::in);
         if (!f.is_open())