Collections build scripts generate incorrect NGINX image when BUILD_ALL=true is not used

[groeges]

Describe the bug
The default behaviour for building collections sets the BUILD_ALL environment variable to true. With this set the build will build all of the collections within Kabanero and adds the built artefacts to the NGINX image. However, if the environment variable is set to false, then only a single collection is built, and only the artefacts for that built collection is added to the NGINX image.

Expected behavior
All required collection artefacts added to the NGINX image

Actual behaviour
Only single collections artefacts are added to the NGINX image.