Editing CI build environment set up by checking out Github workflow

I am trying to use a Github Workflow to build an Android app, but it requires a nonstandard development environment. Specifically, I need to use a file from https://github.com/Reginer/aosp-android-jar.

If I were doing this development manually, I would install Android Studio SDK on my PC, go through its resource files, and replace "android.jar" with the one I downloaded from that repo.

I tried to replicate these steps in a Workflow, but frankly I'm not very familiar with any of this and don't know if what I'm attempting is even possible. This is my (nonfunctional) workflow:

name: Android CI

on: [workflow_dispatch]

jobs:
  build:

    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v4
    - name: set up JDK 17
      uses: actions/setup-java@v4
      with:
        java-version: '17'
        distribution: 'temurin'
        cache: gradle

    - name: Setup Gradle to generate and submit dependency graphs
      uses: gradle/actions/setup-gradle@v4
      with:
        dependency-graph: generate-and-submit

    - name: Grant execute permission for gradlew
      run: chmod +x gradlew

    - name: Replace jar
      shell: bash
      run: |
        pwd >> $GITHUB_STEP_SUMMARY
        odir=$(pwd)
        fpath=$(find . -type f -name 'android.jar')
        echo $fpath >> $GITHUB_STEP_SUMMARY
        cd ${fpath%/*}/
        ls >> $GITHUB_STEP_SUMMARY
        rm android.jar
        curl -o https://github.com/Reginer/aosp-android-jar/raw/refs/heads/main/android-35/android.jar
        cd $odir
      
    - name: Build with Gradle
      run: ./gradlew build
      
    - name: Upload build reports
      uses: actions/upload-artifact@v4
      if: always()
      with:
        name: build-reports
        path: build/reports/