feat(ci): Use input variables for configuring user build

.github/workflows/build-user-config.yml

@@ -2,6 +2,22 @@ name: Reusable user config build
 
 on: 
   workflow_call:
+    inputs:
+      build_matrix_path:
+        description: 'Path to the build matrix file'
+        default: 'build.yaml'
+        required: false
+        type: string
+      config_path:
+        description: 'Path to the config directory'
+        default: 'config'
+        required: false
+        type: string
+      fallback_binary:
+        description: 'Fallback binary format, if no *.uf2 file was built'
+        default: 'bin'
+        required: false
+        type: string
 
 jobs:
   matrix:
@@ -17,8 +33,8 @@ jobs:
       - id: set-matrix
         name: Fetch Build Matrix
         run: |
-          matrix=$(yaml2json build.yaml | jq -c .)
-          yaml2json build.yaml
+          matrix=$(yaml2json ${{ inputs.build_matrix_path }} | jq -c .)
+          yaml2json ${{ inputs.build_matrix_path }}
           echo "::set-output name=matrix::${matrix}"
   build:
     runs-on: ubuntu-latest
@@ -64,14 +80,14 @@ jobs:
             ${{ runner.os }}-build-
             ${{ runner.os }}-
       - name: West Init
-        run: west init -l config
+        run: west init -l ${{ inputs.config_path }}
       - name: West Update
         run: west update
       - name: West Zephyr export
         run: west zephyr-export
       - name: West Build (${{ steps.variables.outputs.display-name }})
         run: |
-          west build -s zmk/app -b ${{ matrix.board }} -- -DZMK_CONFIG=${GITHUB_WORKSPACE}/config ${{ steps.variables.outputs.extra-cmake-args }} ${{ matrix.cmake-args }}
+          west build -s zmk/app -b ${{ matrix.board }} -- -DZMK_CONFIG=${GITHUB_WORKSPACE}/${{ inputs.config_path }} ${{ steps.variables.outputs.extra-cmake-args }} ${{ matrix.cmake-args }}
       - name: ${{ steps.variables.outputs.display-name }} DTS File
         if: ${{ always() }}
         run: |
@@ -85,9 +101,9 @@ jobs:
           if [ -f build/zephyr/zmk.uf2 ]
           then
             cp build/zephyr/zmk.uf2 "build/artifacts/${{ steps.variables.outputs.artifact-name }}.uf2"
-          elif [ -f build/zephyr/zmk.hex ]
+          elif [ -f build/zephyr/zmk.${{ inputs.fallback_binary }} ]
           then
-            cp build/zephyr/zmk.hex "build/artifacts/${{ steps.variables.outputs.artifact-name }}.hex"
+            cp build/zephyr/zmk.${{ inputs.fallback_binary }} "build/artifacts/${{ steps.variables.outputs.artifact-name }}.${{ inputs.fallback_binary }}"
           fi
       - name: Archive (${{ steps.variables.outputs.display-name }})
         uses: actions/upload-artifact@v2