Set git credentials by git-config instead of depending on actions/checkout

Because swift repository is now checkout under ../build/Distribution by
gh-distribute-toolchain and the path can be changed in the future, we
shouldn't assume the path of swift repository. actions/checkout strategy
to pass credentials to git depends on the path, so we manually set the
credentials by ourselves.
The `extraheader` strategy somehow doesn't work now, so we use basic
authentication embedded in the url.

Author: kateinoigakukun

.github/workflows/distribute-toolchain.yml

@@ -23,13 +23,10 @@ jobs:
         with:
           repository: swiftwasm/swiftwasm-build
           path: swiftwasm-build
-      # Checkout swiftwasm/swift also to push tags
-      - uses: actions/checkout@v3
-        with:
-          repository: swiftwasm/swift
-          path: swift
-      - run: git -C swift remote rename origin swiftwasm
-      - run: git -C swift remote add upstream https://github.com/apple/swift.git
+      - name: git config for pushing tags
+        run: git config --global url."https://x-access-token:$GITHUB_TOKEN@github.com/swiftwasm/swift.git".insteadOf "git@github.com:swiftwasm/swift.git"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Setup environment variables
         run: |
           if [[ -n "${{ github.event.inputs.display-name }}" ]]; then