Install llbuild swift bindings

[hartbit]

This PR installs the llbuild Swift bindings in the toolchain so they can be dynamically linked from SwiftPM.

[hartbit]

Please build with following pull request:
swiftlang/swift-llbuild#341

@swift-ci Please Build Toolchain macOS Platform

[aciidgh]

Please build with following pull request:
swiftlang/swift-llbuild#341

@swift-ci Please Build Toolchain Linux Platform

[aciidgh]

Please build with following pull request:
swiftlang/swift-llbuild#341

@swift-ci Please Build Toolchain macOS Platform

[swift-ci]

Linux Toolchain (Ubuntu 16.04)
Download Toolchain
Git Sha - 335290e

Install command
tar zxf swift-PR-17829-36-ubuntu16.04.tar.gz
More info

[swift-ci]

macOS Toolchain
Download Toolchain
Git Sha - 335290e

Install command
tar -zxf swift-PR-17829-46-osx.tar.gz --directory ~/

[gottesmm]

Can you guys add a test that this is installed correctly in the integration repo: https://github.com/apple/swift-integration-tests.

[aciidgh]

@gottesmm do you think such a test will be very valuable? SwiftPM intends to link with this library and will fail to run without it. If that happens, it will be caught by the existing swiftpm tests in the integration repo.

[gottesmm]

@aciidb0mb3r thats good enough for me. I just wanted to make sure that there was /something/.

[hartbit]

Please build with following pull request:
swiftlang/swift-llbuild#341

@swift-ci Please Build Toolchain Linux Platform

[swift-ci]

Linux Toolchain (Ubuntu 16.04)
Download Toolchain
Git Sha - 335290e

Install command
tar zxf swift-PR-17829-37-ubuntu16.04.tar.gz
More info

[aciidgh]

@swift-ci please smoke test