tweak GitHub Actions (#4042)

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       TYPE: ${{ matrix.script }}
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/cache@v1
+      - uses: actions/cache@v2
         with:
           path: tmp
           key: tmp ${{ matrix.script }}

.github/workflows/ufuzz.yml

@@ -2,7 +2,10 @@ name: Fuzzing
 on:
   pull_request:
   schedule:
-    - cron: "0,8,15,23,30,38,45,53 * * * *"
+    - cron: "*/5 * * * *"
+env:
+  CAUSE: ${{ github.event_name }}
+  DATA_URL: https://api.github.com/repos/${{ github.repository }}/actions/workflows/ufuzz.yml/runs?status=queued
 jobs:
   ufuzz:
     strategy:
@@ -16,6 +19,10 @@ jobs:
       - name: Perform fuzzing
         shell: bash
         run: |
+          if [[ $CAUSE == "schedule" ]] && (( `curl -s $DATA_URL | tr -d '\040\011\012\015' | awk -F"queued" '{print NF-1}'` > 3 )); then
+            echo "too many jobs in queue - exiting..."
+            exit
+          fi
           git clone --branch v1.5.4 --depth 1 https://github.com/jasongin/nvs.git ~/.nvs
           while ! timeout 60 bash -c '. ~/.nvs/nvs.sh add 8 && nvs use 8'; do
             cd ~/.nvs