Conditional compilation around using directive breaks source generator.

Reproduction steps:
1. Open the attached project "ReproProj"
2. Observe the Console

Expected result: No Errors exist
Actual result: Error messages “error CS0426: The type name 'InternalCompilerQueryAndHandleData' does not exist in the type 'WheelColliderEditorSystem.CheckJob'” and “'System.ArgumentOutOfRangeException: Non-negative number required. (Parameter 'count')“ are present

Reproducible with: 1.3.9 (6000.0.39f1)

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested

Note:

• Adding this Scripting Symbol in the Player Settings makes the Errors go away: ENABLE_WHEEL_COLLIDER_MATERIAL_INTERACTION