why github gotta be difficult

.github/actions/build-assetbundle/Dockerfile

@@ -1 +1,10 @@
-FROM unityci/editor:ubuntu-2019.4.18f1-windows-mono-3
+ARG UNITY_VERSION=2019.4.18f1
+
+# Source from UnityCI's prebuild unity editor containers
+FROM unityci/editor:${UNITY_VERSION}-windows-mono-3
+
+#Copy entire KSPBuildTools repo into container
+COPY ./ /KSPBuildTools
+
+# Code file to execute when the docker container starts up (`build-assetbundle.sh`)
+ENTRYPOINT ["/KSPBuildTools/.github/actions/build-assetbundle/build-assetbundle.sh"]

.github/actions/build-assetbundle/action.yml

@@ -1,7 +1,22 @@
 name: Build Assetbundle
 description: Build an assetbundle
 
+inputs: 
+  unity-version:
+    description: Full unity version name to build with. e.g. 2019.4.18f1
+    default: '2019.4.18f1'
+
 runs:
-  using: docker
-  image: Dockerfile
+  using: composite
+  steps:
+    - name: Build Docker Container
+      shell: bash
+      run: |
+        docker build -f --platform linux/amd64 --tag build-assetbundle --file ${{ github.action_path }}/Dockerfile --build-arg UNITY_VERSION=${{inputs.unity-version}}
+      working-directory: ${{ github.action_path }}/../../..
+
+    - name: Run Docker Container
+      shell: bash
+      run: |
+        docker run build-assetbundle --volume ${{ github.workspace }}:/github/workspace
 

.github/actions/build-assetbundle/build-assetbundle.sh

@@ -0,0 +1,3 @@
+#!/bin/sh -l
+
+echo "hello"

Editor/AssetBundleBuilder.cs

@@ -0,0 +1,7 @@
+using UnityEditor;
+
+namespace KSPBuildTools.Editor {
+    public class AssetBundleBuilder {
+
+    }
+}

KSPBuildTools.csproj

@@ -40,5 +40,11 @@
   <ItemGroup>
     <Compile Remove="$(MSBuildThisFileDirectory)tests/**" />
     <None Remove="$(MSBuildThisFileDirectory)tests/**" />
+    <Compile Remove="$(MSBuildThisFileDirectory)Editor/**" />
+    <None Remove="$(MSBuildThisFileDirectory)Editor/**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Folder Include=".github\actions\build-assetbundle\" />
   </ItemGroup>
 </Project>