[ci skip] Update GitHub windows_build Action to flag builds as official.

Also do some trivial cleanup of other GitHub Actions.

Author: c-lipka

.github/actions/unix_configure/action.yml

@@ -2,7 +2,7 @@ name: 'Configure POV-Ray for Unix'
 description: 'Run `configure` build step for POV-Ray for Unix'
 
 inputs:
-  configure-options: 
+  configure-options:
     description: 'Additional option for `configure` script'
     required: false
     default: ''

.github/actions/unix_make/action.yml

@@ -2,7 +2,7 @@ name: 'Make POV-Ray for Unix'
 description: 'Run `make` build step for POV-Ray for Unix'
 
 inputs:
-  make-target: 
+  make-target:
     description: 'Target for `make` command'
     required: false
     default: ''

.github/actions/windows_build/action.yml

@@ -2,18 +2,22 @@ name: 'Build POV-Ray for Windows Binary'
 description: 'Build POV-Ray for Windows Binary'
 
 inputs:
-  pov-ray-is-autobuild: 
+  pov-ray-is-autobuild:
     description: 'POV_RAY_IS_AUTOBUILD value'
     required: true
     default: '1'
-  pov-ray-build-id: 
+  pov-ray-special-sauce:
+    description: 'Special sauce, e.g. for flagging a build as official'
+    required: false
+    default: ''
+  pov-ray-build-id:
     description: 'POV_RAY_BUILD_ID value'
     required: true
-  built-by: 
+  built-by:
     description: 'BUILT_BY value'
     required: true
     default: 'GitHub'
-  solution: 
+  solution:
     description: 'subdirectory of `windows` in which `povray.sln` is located'
     required: true
   configuration:
@@ -24,11 +28,11 @@ inputs:
     description: 'solution platform to build'
     required: false
     default: 'x64'
-  toolset: 
+  toolset:
     description: 'Platform toolset version'
     required: false
     default: 'v140'
-  msbuild-options: 
+  msbuild-options:
     description: 'additional MSBuild options'
     required: false
     default: ''
@@ -41,6 +45,7 @@ runs:
       $env:PovBuildDefs  = 'POV_RAY_IS_AUTOBUILD=${{ inputs.pov-ray-is-autobuild }};'
       $env:PovBuildDefs += 'POV_RAY_BUILD_ID="${{ inputs.pov-ray-build-id }}";'
       $env:PovBuildDefs += 'BUILT_BY="${{ inputs.built-by }}";'
+      $env:PovBuildDefs += '${{ inputs.pov-ray-special-sauce }}'
       msbuild `
         /t:Rebuild /m `
         /p:Configuration=${{ inputs.configuration }} `