scripts: user-specified container build params

This allows a developer who invokes scripts/container.image.build.bash to
specify arbitrary parameters for the underlying builder.

e.g. "--no-cache", which is a better way of avoiding using the local build
cache than bumping the CI-focussed build ARG at the top of
container/build/Containerfile.

scripts/container.image.build.bash

@@ -3,7 +3,8 @@ set -euo pipefail
 
 # container.image.build.bash builds an image from a stage defined in
 # container/build/Containerfile, and tags it as "ynr:$image".
-image="$1"
+image="$1"; shift
+args="$@"
 
 # Change to the directory above the directory containing this script.
 cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/.."
@@ -17,4 +18,4 @@ else
 fi; set -u
 
 # Build the image.
-"$builder" build --target "$image" --tag "ynr:$image" -f container/build/Containerfile .
+"$builder" build --target "$image" --tag "ynr:$image" -f container/build/Containerfile $args .