Easier multi-arch or multi-version builds

docs/developing.md

@@ -13,19 +13,32 @@ You need to ensure you have the following tools installed:
 For running the Kubernetes tests, a Kubernetes environment is needed, for example [Minikube](https://github.com/kubernetes/minikube) or [IBM Cloud Private](https://www.ibm.com/cloud-computing/products/ibm-cloud-private/).
 
 ## Building a production image
+This procedure works for building the MQ Continuous Delivery release, on `x86_64`, `ppc64le` and `s390x` architectures.
 
-1. Download MQ from IBM Passport Advantage, and place the downloaded file (for example, `CNLE4ML.tar.gz` for MQ V9.0.4) in the `downloads` directory
+1. Download MQ from IBM Passport Advantage, and place the downloaded file (for example, `CNLE4ML.tar.gz` for MQ V9.0.4 on x86_64 architecture) in the `downloads` directory
 2. Run `make build-advancedserver`
 
+You can build a different version of MQ by setting the `MQ_VERSION` environment variable, for example:
+
+```bash
+MQ_VERSION=9.0.3.0 make build-advancedserver
+```
+
 ## Running the tests
 There are three main sets of tests:
 
-1. Unit tests
+1. Unit tests, which are run during a build
 2. Docker tests, which test a complete Docker image, using the Docker API
 3. Kubernetes tests, which test the Helm charts (and the Docker image) via [Helm](https://helm.sh)
 
-### Running the tests
-The unit and Docker tests can be run locally.  For example:
+### Running the Docker tests
+The Docker tests can be run locally.  Before you run them for the first time, you need to download the test dependencies:
+
+```
+make deps
+```
+
+You can then run the tests, for example:
 
 ```
 make test-devserver
@@ -37,7 +50,7 @@ or:
 make test-advancedserver
 ```
 
-### Running the tests with code coverage
+### Running the Docker tests with code coverage
 You can produce code coverage results from the Docker tests by running the following:
 
 ```