swift-build-tool is not bundled in the 2.2 release

Author: mxcl

README.md

@@ -54,6 +54,8 @@ following options:
             swiftpm/Utilities/bootstrap --swiftc path/to/snapshot/usr/bin/swiftc --sbt path/to/snapshot/usr/bin/swift-build-tool
 
    `swiftc` and `swift-build-tool` are both executables provided as part of Swift downloadable snapshots, *they are **not** built from the sources in this repository*.
+   
+   Please note, that the 2.2 release snapshot does not come with `swift-build-tool`, either download the *development* snapshot or build your own copy of `swift-llbuild`.
 
 3. Using the Xcode Project in [Support](Support), this option requires:
    * Xcode 7.3 (beta)