package: rewrite build scripts (#701)

not using bash gives us more flexibility and significantly reduces build
times via parallelism. Additionally this includes support for GitHub
Actions which also significantly reduces build times.

.github/workflows/build.yml

@@ -0,0 +1,58 @@
+on:
+  workflow_dispatch:
+    inputs:
+      FORCE_BUILD:
+        description: "List of plugins to build, or 'ALL'"
+        required: false
+      COMMIT_RANGE:
+        description: "Commit range to build 1234abc..5689def"
+        required: false
+  push:
+  pull_request:
+jobs:
+  execute:
+    # any forks that predate this repo having an action will have actions
+    # enabled by default, which will fail in a lot of cases because the branch
+    # is new, which makes the differential build fail
+    if: github.event_name != 'push' || github.repository_owner == 'runelite'
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - uses: actions/setup-java@v1
+      with:
+        java-version: 11
+    - uses: actions/cache@v2
+      with:
+        path: |
+          ~/.gradle/caches/
+          ~/.gradle/wrapper/
+        key: package-2.0.0
+    - name: prepare
+      run: |
+        pushd package
+        ./gradlew --build-cache prep
+        popd
+    - name: build
+      env:
+        REPO_CREDS: ${{ secrets.REPO_CREDS }}
+        REPO_ROOT: ${{ secrets.REPO_ROOT }}
+        SIGNING_KEY: ${{ secrets.SIGNING_KEY }}
+        # workflow_dispatch
+        FORCE_BUILD: ${{ github.event.inputs.FORCE_BUILD }}
+        COMMIT_RANGE: ${{ github.event.inputs.COMMIT_RANGE }}
+        # push
+        COMMIT_BEFORE: ${{ github.event.before }}
+        COMMIT_AFTER: ${{ github.event.after }}
+        # pull_request
+        PR_BEFORE: ${{ github.event.pull_request.base.sha }}
+        PR_AFTER: ${{ github.event.pull_request.head.sha }}
+        PACKAGE_IS_PR: ${{ github.event_name == 'pull_request' }}
+      run: |
+        if $PACKAGE_IS_PR; then
+          export PACKAGE_COMMIT_RANGE="$PR_BEFORE..$PR_AFTER"
+        else
+          export PACKAGE_COMMIT_RANGE="${COMMIT_RANGE:-${COMMIT_BEFORE:+$COMMIT_BEFORE..$COMMIT_AFTER}}"
+        fi
+        java -XX:+UseParallelGC -jar package/package/build/libs/package.jar