Summary:
If FSUIPC is configured, its support will be enabled in swift
and disabled otherwise.
Ref T91
Reviewers: #swift_pilot_client, msutcliffe
Reviewed By: #swift_pilot_client, msutcliffe
Subscribers: msutcliffe, jenkins, kbasan
Maniphest Tasks: T91
Differential Revision: https://dev.swift-project.org/D28
CBuildConfig including private keys etc. should not be part of a
public library API. Therefore link it into a static library, which
is not available to end users.
refs #645
