scope_exit: Make constexpr

Allows the use of the macro in constexpr-contexts.
Also avoids some potential problems when nesting braces inside it.

src/core/loader/nca.cpp

@@ -118,7 +118,9 @@ ResultStatus AppLoader_NCA::VerifyIntegrity(std::function<bool(size_t, size_t)>
     mbedtls_sha256_starts_ret(&ctx, 0);
 
     // Ensure we maintain a clean state on exit.
-    SCOPE_EXIT({ mbedtls_sha256_free(&ctx); });
+    SCOPE_EXIT {
+        mbedtls_sha256_free(&ctx);
+    };
 
     // Declare counters.
     const size_t total_size = file->GetSize();