This fixes loading SwiftShader in Chrome and in Renderdoc. Requires
explicitly specifying the ICD and module directories ("./" or ".\\").

Bug: angleproject:3876
Bug: b/142756865
Change-Id: I9183c81cb0e8ac117fc5d7a8f2048dc0555632c4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1864315Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>