concat-deps: fix build with gcc -fsanitize=... -std=gnu89

Apparently Clang C89 mode is sloppily implemented and allows this.

Change-Id: I78ef943bc4c5f8590dae8879dad65ad9fbe9a9bb

solenv/bin/concat-deps.c

@@ -1174,11 +1174,14 @@ const char *env_str;
 #endif
     }
 #if !ENABLE_RUNTIME_OPTIMIZATIONS
+    {
+        size_t i;
         hash_destroy(dep_hash);
-    for (size_t i = 0; i != file_load_buffer_count; ++i)
+        for (i = 0; i != file_load_buffer_count; ++i)
         {
             free(file_load_buffers[i]);
         }
+    }
 #endif
     return rc;
 }