Also fall back to LLVM 3.0 automatically if C++11 is not supported.

Bug b/115344057
Bug b/116540140

Change-Id: Ied0bfa17fcdc82f1181704fd63eda5c312b8380e
Reviewed-on: https://swiftshader-review.googlesource.com/c/21510Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>