alpha: add rpms to sdk

To create an early-access version of twoliter build variant, we need
an SDK that contains the Bottlerocket rpms. This script and Dockerfile
creates it.

local/README.md

@@ -0,0 +1,4 @@
+
+# The Local Directory
+
+This directory is for scripts involved with building and testing Twoliter.

local/alpha-sdk.dockerfile

@@ -0,0 +1,3 @@
+ARG SDK
+FROM $SDK
+COPY build/rpms/ /twoliter/alpha/build/rpms/

local/alpha-sdk.sh

@@ -0,0 +1,131 @@
+#!/usr/bin/env bash
+
+# The Alpha milestone (i.e. preceding Beta) represents a version of Twoliter that can build a
+# customized variant before Kits have been implemented. See:
+# - https://github.com/bottlerocket-os/twoliter/issues/74
+# - https://github.com/bottlerocket-os/twoliter/issues/56
+#
+# This script builds a bottlerocket variant, then copies certain contents of the Bottlerocket build
+# directory into a layer added to the SDK. Twoliter's build variant command will expect these to be
+# available in the SDK at `/twoliter/alpha` until Kits have been implemented.
+
+# The directory this script is located in.
+script_dir=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+
+#
+# Common error handling
+#
+
+exit_trap_cmds=()
+
+on_exit() {
+    exit_trap_cmds+=( "$1" )
+}
+
+run_exit_trap_cmds() {
+    for cmd in "${exit_trap_cmds[@]}"; do
+        eval "${cmd}"
+    done
+}
+
+trap run_exit_trap_cmds EXIT
+
+warn() {
+    >&2 echo "Warning: $*"
+}
+
+bail() {
+    if [[ $# -gt 0 ]]; then
+        >&2 echo "Error: $*"
+    fi
+    exit 1
+}
+
+usage() {
+    cat <<EOF
+Usage: $0 --bottlerocket-dir DIR [--variant VARIANT] [--arch ARCH] --sdk-version SDK_VERSION [--sdk-name SDK_NAME] [ --sdk-registry SDK_REGISTRY ] [-h]
+
+    --bottlerocket-dir            The directory of the Bottlerocket checkout that we will build.
+    --variant                     The Bottlerocket variant that we will build.
+    --arch                        The target architecture that we will build Bottlerocket for.
+                                  Defaults to this host's architecture.
+    --sdk-version                 The version of the Bottlerocket SDK to use when building packages
+                                  and to use as the base for the Twoliter alpha-sdk. For example if
+                                  the SDK version is v0.50.0 then --sdk-version should be the same
+                                  (i.e. with the v prefix).
+    --sdk-name                    The name prefix of the SDK. For example, in this following string
+                                  'bottlerocket' is the SDK name:
+                                  public.ecr.aws/bottlerocket/bottlerocket-sdk-x86_64:v0.50.0
+                                  Note that the suffix '-sdk' is assumed and added to the name,
+                                  which is just 'bottlerocket'
+    --sdk-registry                The namespace or Docker registry where the SDK is found. For
+                                  example, in the following string 'public.ecr.aws' is the
+                                  registry:
+                                  public.ecr.aws/bottlerocket/bottlerocket-sdk-x86_64:v0.50.0
+    --alpha-sdk-tag               The tag to give the Docker image that this script produces.
+    -h, --help                    show this help text
+
+EOF
+}
+
+usage_error() {
+    >&2 usage
+    bail "$1"
+}
+
+#
+# Parse arguments
+#
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --bottlerocket-dir)
+            shift; bottlerocket_dir=$1 ;;
+        --variant)
+            shift; variant=$1 ;;
+        --arch)
+            shift; arch=$1 ;;
+        --sdk-version)
+            shift; sdk_version=$1 ;;
+        --sdk-name)
+            shift; sdk_name=$1 ;;
+        --sdk-registry)
+            shift; sdk_registry=$1 ;;
+        --tag)
+            shift; tag=$1 ;;
+        -h|--help)
+            usage; exit 0 ;;
+        *)
+            usage_error "Invalid option '$1'" ;;
+    esac
+    shift
+done
+
+set -e
+
+[[ -n ${bottlerocket_dir} ]] || usage_error 'required: --bottlerocket-dir'
+[[ -n ${bottlerocket_dir} ]] || usage_error 'required: --sdk-version'
+
+variant="${variant:=aws-dev}"
+arch="${arch:=$(uname -m)}"
+sdk_name="${sdk_name:=bottlerocket}"
+sdk_registry="${sdk_registry:=public.ecr.aws/bottlerocket}"
+tag="${tag:=twoliter.alpha/bottlerocket-sdk}"
+
+cd "${bottlerocket_dir}"
+
+cargo make \
+    -e "BUILDSYS_VARIANT=${variant}" \
+    -e "BUILDSYS_ARCH=${arch}" \
+    -e "BUILDSYS_SDK_NAME=${sdk_name}" \
+    -e "BUILDSYS_SDK_VERSION=${sdk_version}" \
+    -e "BUILDSYS_SDK_REGISTRY=${sdk_registry}" \
+    build-variant
+
+sdk="${sdk_registry}/${sdk_name}-sdk-${arch}:${sdk_version}"
+
+docker build \
+  --tag "${tag}" \
+  --build-arg "SDK=${sdk}" \
+  --file "${script_dir}/alpha-sdk.dockerfile" \
+  "${bottlerocket_dir}"