Was wrongly assuming that if ..\deqp exists, the build directory must
be deqp\build.

Change-Id: I0e071565d9c41940efbcd4453de70f2994ad1be5
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27652Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>