(misc) Create a GitHub Action for building the server JAR

.github/workflows/build.yml

@@ -0,0 +1,44 @@
+name: Build LunarCore
+on:
+  workflow_dispatch: ~
+  push:
+    paths:
+      - "**.java"
+    branches:
+      - main
+      - development
+  pull_request:
+    paths:
+      - "**.java"
+    types:
+      - opened
+      - synchronize
+      - reopened
+jobs:
+  Build:
+    runs-on: ubuntu-latest
+    steps:
+        - name: Checkout
+          uses: actions/checkout@v3
+        - name: Setup Java
+          uses: actions/setup-java@v3
+          with:
+            distribution: temurin
+            java-version: '17'
+        - name: Cache gradle files
+          uses: actions/cache@v2
+          with:
+            path: |
+              ~/.gradle/caches
+              ~/.gradle/wrapper
+              ./.gradle/loom-cache
+            key: ${{ runner.os }}-gradle-${{ hashFiles('*.gradle', 'gradle.properties', '**/*.accesswidener') }}
+            restore-keys: |
+              ${{ runner.os }}-gradle-
+        - name: Run Gradle
+          run: ./gradlew && ./gradlew jar
+        - name: Upload build
+          uses: actions/upload-artifact@v3
+          with:
+            name: LunarCore
+            path: LunarCore-*.jar

build.gradle

@@ -104,7 +104,9 @@ configurations.all {
 }
 
 clean {
-    delete protobuf.generatedFilesBaseDir
+    if (shouldGenerateProto) {
+        delete protobuf.generatedFilesBaseDir
+    }
 }
 
 application {