Update swift-ci/README to add missing required build parameters for using the CI Dockerfiles. Also normalize some whitespace.

Author: gwynne

swift-ci/README.md

@@ -2,22 +2,17 @@
 
 Swift.org uses Docker based virtual build environment to build & qualify Swift toolchains on Linux.
 
-The Continuous Integration system uses the Dockerfiles in this directory to define the virtual build environment,
-then runs the build and qualification steps inside a docker container based on the image.
+The Continuous Integration system uses the Dockerfiles in this directory to define the virtual build environment, then runs the build and qualification steps inside a docker container based on the image.
 
 ## Directory Structure
 
-The Dockerfiles used for Continuous Integration are layed out under the top level `swift-ci` directory.
-Under that, we have a directory for each of the target branches, e.g.
-Continuous Integration for Swift's `master` branch uses the `swift-ci/master` Dockerfiles.
+The Dockerfiles used for Continuous Integration are layed out under the top level `swift-ci` directory. Under that, we have a directory for each of the target branches, e.g. Continuous Integration for Swift's `main` branch uses the `swift-ci/master` Dockerfiles.
 
 There is also a specific directory (`swift-docc-render`) for the Dockerfile used to build Swift-DocC-Render. Swift-DocC-Render builds separately from the rest of the projects in the Swift toolchain and ships a pre-built copy for use in the toolchain in the Swift-DocC-Render-Artifact repository.
 
 ## Continuous Integration
 
-This system is designed to support many distributions.
-Once a working Dockerfile is added to this repository,
-we set up Continuous Integration jobs to produce toolchains for the distribution and publish them on Swift.org.
+This system is designed to support many distributions. Once a working Dockerfile is added to this repository, we set up Continuous Integration jobs to produce toolchains for the distribution and publish them on Swift.org.
 
 ## Local development & testing
 
@@ -27,7 +22,7 @@ First build & tag the Dockerfile:
 docker build -f <dockerfile path> . -t <some tag>
 ```
 
-Next run the Swift build using that Docker image
+Next, run the Swift build using that Docker image:
 
 ```bash
 docker run \
@@ -37,7 +32,7 @@ docker run \
   -v <some docker volume name>:/home/build-user \
   -w /home/build-user/ \
   <docker image tag from above> \
-  /bin/bash -lc "cp -r /source/* /home/build-user/; ./swift/utils/build-script --preset buildbot_linux"
+  /bin/bash -lc "cp -r /source/* /home/build-user/; ./swift/utils/build-script --preset buildbot_linux install_destdir=/home/build-user/swift-install installable_package=/home/build-user/swift-DEVELOPMENT-SNAPSHOT-$(date +'%F')-a.tar.gz"
 ```
 
 ## Contributions