ci: migrate workflows to zmk-docker

Leverages the new zmk-build-arm Docker image published by the zmk-docker project.  Reduces build times, enhances DevOps capabilities, and tightly couples CI build container with the dev container.

PR: #481

.github/workflows/build.yml

@@ -13,6 +13,8 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    container:
+      image: zmkfirmware/zmk-build-arm:2.3
     strategy:
       matrix:
         board:
@@ -82,25 +84,13 @@ jobs:
         timeout-minutes: 2
         continue-on-error: true
       - name: West init
-        uses: "docker://zmkfirmware/zephyr-west-action-arm:latest"
-        id: west-init
-        with:
-          args: 'init "-l app"'
+        run: west init -l app
       - name: West update
-        uses: "docker://zmkfirmware/zephyr-west-action-arm:latest"
-        id: west-update
-        with:
-          args: "update"
+        run: west update
       - name: West config Zephyr base
-        uses: "docker://zmkfirmware/zephyr-west-action-arm:latest"
-        id: west-config
-        with:
-          args: 'config "--global zephyr.base-prefer configfile"'
+        run: west config --global zephyr.base-prefer configfile
       - name: West Zephyr export
-        uses: "docker://zmkfirmware/zephyr-west-action-arm:latest"
-        id: west-zephyr-export
-        with:
-          args: "zephyr-export"
+        run: west zephyr-export
       - name: Prepare variables
         id: variables
         run: |
@@ -117,10 +107,7 @@ jobs:
           echo ::set-output name=shield-arg::${SHIELD_ARG}
           echo ::set-output name=artifact-name::${ARTIFACT_NAME}
       - name: West build
-        uses: "docker://zmkfirmware/zephyr-west-action-arm:latest"
-        id: west-build
-        with:
-          args: 'build "-s app -b ${{ matrix.board }} -- ${{ steps.variables.outputs.shield-arg }}'
+        run: west build -s app -b ${{ matrix.board }} -- ${{ steps.variables.outputs.shield-arg }}
       - name: Archive build
         uses: actions/upload-artifact@v2
         with: