ci: update musl-cross download link (bnb-chain#3147)

Author: zzzckck

.github/workflows/release.yml

@@ -50,7 +50,7 @@ jobs:
         if: matrix.os == 'ubuntu-latest'
         run: |
           go mod download
-          wget https://musl.cc/x86_64-linux-musl-cross.tgz
+          wget ${{ env.MUSL_CROSS_URL }}/x86_64-linux-musl-cross.tgz
           tar -xvf ./x86_64-linux-musl-cross.tgz
           GIT_COMMIT=$(git rev-parse HEAD)
           GIT_COMMIT_DATE=$(git log -n1 --pretty='format:%cd' --date=format:'%Y%m%d')
@@ -70,7 +70,7 @@ jobs:
         if: matrix.os == 'ubuntu-latest'
         run: |
           go mod download
-          wget https://musl.cc/aarch64-linux-musl-cross.tgz
+          wget ${{ env.MUSL_CROSS_URL }}/aarch64-linux-musl-cross.tgz
           tar -xvf ./aarch64-linux-musl-cross.tgz
           GIT_COMMIT=$(git rev-parse HEAD)
           GIT_COMMIT_DATE=$(git log -n1 --pretty='format:%cd' --date=format:'%Y%m%d')