Address a bunch of clang-tidy complaints.

There were a bunch more unreasonable/incorrect ones, but these ones
seemed legit. Nothing very interesting, though.

Bug: N/A
Test: ran tests, benchmarks
Change-Id: If66971194d4a7b4bf6d0251bedb88e8cdc88a76f
diff --git a/tests/utils.h b/tests/utils.h
index a5783af..3f4218e 100644
--- a/tests/utils.h
+++ b/tests/utils.h
@@ -180,10 +180,10 @@
     return const_cast<char**>(env_.data());
   }
 
-  void SetArgs(const std::vector<const char*> args) {
+  void SetArgs(const std::vector<const char*>& args) {
     args_ = args;
   }
-  void SetEnv(const std::vector<const char*> env) {
+  void SetEnv(const std::vector<const char*>& env) {
     env_ = env;
   }