How to reproduce:
1. Create a new Unity project with version 2018.3.0a5 or older
2. Build the empty project into a player
3. Check Editor.log for build results - assemblies were reloaded after the build was completed
4. Create a new Unity project with version 2018.3.0a6 or newer
5. Build the empty project into a player
6. Check Editor.log for build results

Expected result: the log indicates that assemblies were reloaded after the build was completed
Actual result: there is no mention of an assembly reload after the build was completed

Reproducible with: 2018.3.0a6, 2018.3.3f1, 2019.1.0a14, 2019.2.0a2
Not reproducible with: 2017.4.19f1, 2018.3.0a5

Notes:
It was possible to bypass the assembly reload before 2018.3.0a6 by building the project in batchmode, altering scripting define symbols before starting the build and restoring them to what they were before building was complete