The ICD_LIBRARY_PATH variable needs to be double-escaped - once for CMake, and another for the actual .json file.

Bug b/116336664

Change-Id: I8fd68c6a030b689e6432828ec5f1cf938c2a0d45
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34455Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Ben Clayton <bclayton@google.com>