ENH: Add platform-specific package install inputs and OS selection

Add optional inputs to the CXX build workflow:

- apt-packages: Install system packages on Linux (apt-get)
- brew-packages: Install system packages on macOS (brew)
- choco-packages: Install system packages on Windows (choco)
- os-list: JSON array of runner OS labels to build on, allowing
  modules to disable platforms that cannot work

Update README with:
- Simplified example using secrets: inherit instead of explicit
  secrets block (avoids YAML errors from empty secrets:)
- Example for modules with external system dependencies
- Updated workflow ref from @main to @v5.4.6

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hjmjohnson

.github/workflows/build-test-cxx.yml

@@ -30,14 +30,31 @@ on:
         # example: MeshToPolyData@3ad8f08:BSplineGradient@0.3.0
         required: false
         type: string
+      apt-packages:
+        description: 'Space-separated list of apt packages to install on Linux runners before building (e.g. libopenslide-dev libfftw3-dev)'
+        required: false
+        type: string
+      brew-packages:
+        description: 'Space-separated list of Homebrew packages to install on macOS runners before building (e.g. openslide libomp)'
+        required: false
+        type: string
+      choco-packages:
+        description: 'Space-separated list of Chocolatey packages to install on Windows runners before building'
+        required: false
+        type: string
+      os-list:
+        description: 'JSON-formatted array of runner OS labels to build on (default: all platforms)'
+        required: false
+        type: string
+        default: '["ubuntu-22.04", "windows-2022", "macos-15-intel", "macos-15"]'
 
 jobs:
   build-test-cxx:
     runs-on: ${{ matrix.os }}
     strategy:
       max-parallel: 3
       matrix:
-        os: [ubuntu-22.04, windows-2022, macos-15-intel, macos-15]
+        os: ${{ fromJSON(inputs.os-list) }}
         include:
           - os: ubuntu-22.04
             c-compiler: "gcc"
@@ -65,6 +82,22 @@ jobs:
       with:
         large-packages: false
 
+    - name: Install system packages (Linux)
+      if: inputs.apt-packages != '' && runner.os == 'Linux'
+      run: |
+        sudo apt-get update -qq
+        sudo apt-get install -y -qq ${{ inputs.apt-packages }}
+
+    - name: Install system packages (macOS)
+      if: inputs.brew-packages != '' && runner.os == 'macOS'
+      run: |
+        brew install ${{ inputs.brew-packages }}
+
+    - name: Install system packages (Windows)
+      if: inputs.choco-packages != '' && runner.os == 'Windows'
+      run: |
+        choco install -y ${{ inputs.choco-packages }}
+
     - name: Set up Python 3.11
       uses: actions/setup-python@v5
       with:

README.md

@@ -87,14 +87,38 @@ on: [push,pull_request]
 
 jobs:
   cxx-build-workflow:
-    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@main
+    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@v5.4.6
+
+  python-build-workflow:
+    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-package-python.yml@v5.4.6
+    secrets: inherit
+```
+
+> **Note:** `secrets: inherit` passes all repository secrets (including `pypi_password`)
+> to the reusable workflow. This is simpler than explicitly listing each secret and avoids
+> YAML errors from empty `secrets:` blocks. Alternatively, you can pass secrets explicitly:
+> ```yaml
+>     secrets:
+>       pypi_password: ${{ secrets.pypi_password }}
+> ```
+
+#### Modules with external system dependencies
+
+Modules that require system libraries not available on standard runners can use
+the `apt-packages`, `brew-packages`, `choco-packages`, and `os-list` inputs:
+
+```yaml
+jobs:
+  cxx-build-workflow:
+    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-cxx.yml@v5.4.6
     with:
-      itk-cmake-options: '-DITK_BUILD_DEFAULT_MODULES:BOOL=OFF -DITKGroup_Core:BOOL=ON'
+      apt-packages: 'libopenslide-dev'
+      brew-packages: 'openslide'
+      os-list: '["ubuntu-22.04", "macos-15-intel", "macos-15"]'
 
   python-build-workflow:
-    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-package-python.yml@main
-    secrets:
-      pypi_password: ${{ secrets.pypi_password }}
+    uses: InsightSoftwareConsortium/ITKRemoteModuleBuildTestPackageAction/.github/workflows/build-test-package-python.yml@v5.4.6
+    secrets: inherit
 ```
 
 The example above can be broken down line by line: