package: avoid rebuilding plugins with compatible apis

we have to do this as part of a compiler plugin, and not by just looking
at the classes' bytecode, because jls§13.1 requires inlining of certain
constant values, so references to these will not be present in the
bytecode.

.github/workflows/build.yml

@@ -7,8 +7,13 @@ on:
       COMMIT_RANGE:
         description: "Commit range to build 1234abc..5689def"
         required: false
+      API_FILES_VERSION:
+        description: "RuneLite version to use .api files from"
+        required: false
   push:
   pull_request:
+env:
+  CACHE_VERSION: 2.1.0
 jobs:
   build:
     # any forks that predate this repo having an action will have actions
@@ -29,7 +34,9 @@ jobs:
         path: |
           ~/.gradle/caches/
           ~/.gradle/wrapper/
-        key: package-2.0.10
+        key: package-${{ env.CACHE_VERSION }}-${{ hashFiles('runelite.version') }}
+        restore-keys: |
+          package-${{ env.CACHE_VERSION }}-
     - name: prepare
       run: |
         pushd package
@@ -43,6 +50,7 @@ jobs:
         # workflow_dispatch
         FORCE_BUILD: ${{ github.event.inputs.FORCE_BUILD }}
         COMMIT_RANGE: ${{ github.event.inputs.COMMIT_RANGE }}
+        API_FILES_VERSION: ${{ github.event.inputs.API_FILES_VERSION }}
         # push
         COMMIT_BEFORE: ${{ github.event.before }}
         COMMIT_AFTER: ${{ github.event.after }}
@@ -68,6 +76,7 @@ jobs:
   upload:
     if: (github.event_name != 'push' || github.repository_owner == 'runelite') && github.event_name != 'pull_request'
     needs: build
+    concurrency: upload
     runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
@@ -82,7 +91,7 @@ jobs:
         path: |
           ~/.gradle/caches/
           ~/.gradle/wrapper/
-        key: upload-2.0.10
+        key: upload-${{ env.CACHE_VERSION }}
     - uses: actions/download-artifact@v2
       with:
         name: manifest_diff