When we applied BACKPORT-3018 (for SERVER-35078), we couldn't build all phases of the SDK build with bitcode enabled due to SERVER-29908 not being backported to 4.0. As a compromise, we just built the install-sdk phase with bitcode, and then rebuilt without it when building the tests.

Once SERVER-29908 is backported to 4.0, we should go back to always using bitcode for all phases of the 4.0 build.