When you switch platforms from Standalone to Universal Windows Platform, the PlayerSettings->XRSettings->Virtual Reality SDKs from Standalone are still reported by XRSettings.supportedDevices during playmode. This can lead to confusion for users who are trying to target multiple platforms.

Reproduced in 2018.2.0a5, 2018.1.0b10, and 2017.3.1f1

Steps to reproduce:
1. Open the attached project LegacyXRInput.zip
2. Open the TrackedPoseDriver scene
3. In Build Settings, switch to the "PC, Mac & Linux Standalone" build platform.
4. Set PlayerSettings->XRSettings->Virtual Reality Supported to enabled
5. Add the OpenVR and Oculus SDKs
6. In Build Settings, switch to the "Universal Windows Platform" build platform.
7. Set PlayerSettings->XRSettings->Virtual Reality Supported to enabled
8. Add the Windows Mixed Reality SDK.
9. Press play. Observe that the reported Supported Devices still contains the VR platforms from the Standalone platform.

Expected Results: Only report the platform supported VR SDKs.
Observed Results: Report the VR supported SDKs that were set while targeting a different build platform.