Reproduction steps:
1. Open the attached project;
2. Build the scene "ARtest01" on Android or Standalone platform;

Actual result: Unity crashes in <GetScriptCompilationDefines> during the building process.
Expected result: Unity should not crash and should build the project.

Note: Editor crashes, when the project has Vuforia plugin. If Vuforia folder is deleted, Unity does not crash.

Reproduced with: 5.6.1p2
Not reproducible with: 5.6.0f1, 5.6.0p3, 5.6.1f1, 5.6.1p1
Regression introduced in 5.6.1p2

Fixed in 5.6.1p3, 2017.1.0b9, 2017.2.0a3