Retry downloading dependencies twice in CI

.github/workflows/check.yaml

@@ -46,8 +46,21 @@ jobs:
             --target x86_64-unknown-linux-musl
 
       - name: Fetch dependencies (retry)
+        id: fetch-2
         uses: actions-rs/cargo@v1
         if: steps.fetch.outcome == 'failure'
+        continue-on-error: true
+        with:
+          command: fetch
+          args: |-
+            -Zmultitarget
+            --target x86_64-apple-darwin
+            --target x86_64-pc-windows-msvc
+            --target x86_64-unknown-linux-musl
+
+      - name: Fetch dependencies (second retry)
+        uses: actions-rs/cargo@v1
+        if: steps.fetch.outcome == 'failure' && steps.fetch-2.outcome == 'failure'
         with:
           command: fetch
           args: |-