Unity version: 2018.2.0f2

When using HDRP on Mac OS X 10.12.5, the user is able to create a build, even though the error message says `Platform Mac OS X 10.12.5 with device Metal is not supported, no rendering will occur`.

Expected result:
The build should fail

Actual result:
The build succeeds with no rendering, so the player is completely black.

Steps to repro:
1) On a Mac 10.12 machine, create or load a HDRP project (I used Book Of The Dead)
2) Observe errors in the console
3) Set off a build
4) Observe that the build succeeds, despite the errors
5) The built player has no rendering, and is completely black