Repro steps:

1. Open user attached project Scene1.
2. Build project
-Notice output of console: build index of active scene is equal to -1

Expected result: buildIndex of currently processed active scene is equal to its build index;
Actual result: build index of currently processed active scene is equal to -1;

Build index is set to -1 for scenes that are active during build.
Workaround: make a new scene, don't include it to build list, make it active during build.

Reproduced on: 5.3.5f1, 5.4.0f1, 5.4.0f3

Note: on 5.3.5f1 build index is equal to -1 on all scenes.