Installation instructions for a SNAPHOT with XCTest support

install-swift-test-linux.md

1. Install the latest snapshot:

wget https://swift.org/builds/development/ubuntu1510/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a-ubuntu15.10.tar.gz

2. Set an environment variable pointing to your snapshot

export SWIFT_PATH=/home/rfdickerson/linux-swift-testing/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a-ubuntu15.10

3. Download Swift Package Manager repository:

git clone https://github.com/apple/swift-package-manager.git

4. Build the Package Manager:

cd swift-package-manager

Utilities/bootstap --swiftc ${SWIFT_PATH}/usr/bin/swiftc \ 
  --sbt ${SWIFT_PATH}/usr/bin/sbt \ 
  --prefix ${SWIFT_PATH}/usr \ 
  install

cd ..

5. Download XCTest framework:

git clone https://github.com/apple/swift-corelibs-xctest

6. Build the XCTest framework:

cd swift-corelibs-xctest
./build_script.py \
  --swiftc="${SWIFT_PATH}/usr/bin/swiftc" \
  --build-dir="/tmp/XCTest_build" \
  --library-install-path="${SWIFT_PATH}/usr/lib/swift/linux" \
  --module-install-path="${SWIFT_PATH}/usr/lib/swift/linux/x86_64"
  ```
  
7. Download libDispatch

```shell
git submodule init && \
git submodule update && \
sh ./autogen.sh && \
./configure --with-swift-toolchain=${SWIFT_PATH}/usr \
--prefix=${SWIFT_PATH}/usr && make && sudo make install