.github/workflows: Fork checks for jobs/steps that need creds

.github/workflows/docker.yml

@@ -6,6 +6,7 @@ on:
       - master
 jobs:
   build:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     runs-on: ubuntu-16.04
     steps:
     - name: Checkout

.github/workflows/linux.yml

@@ -101,7 +101,7 @@ jobs:
   upload:
     runs-on: ubuntu-18.04
     needs: [build, test]
-    if: github.repository == 'livepeer/go-livepeer'
+    if: github.event.pull_request.head.repo.full_name == github.repository
     steps:
       - name: Checkout
         uses: actions/checkout@v2

.github/workflows/windows.yml

@@ -25,6 +25,7 @@ jobs:
       shell: msys2 {0}
       run: ./ci_env.sh make livepeer livepeer_cli livepeer_bench livepeer_router
     - name: Upload build
+      if: github.event.pull_request.head.repo.full_name == github.repository
       shell: msys2 {0}
       env: 
         GHA_REF: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.ref || github.ref }}