update build.yml

Author: Kodp

.github/workflows/build.yml

@@ -43,13 +43,14 @@ jobs:
           git clone https://github.com/LearningOS/rCore-Tutorial-Checker-2025S.git ci-user
           git clone https://github.com/LearningOS/rCore-Tutorial-Test-2025S.git ci-user/user
 
-          # --- 使用环境变量强制指定镜像源 ---
-          export CARGO_SOURCE_CRATES_IO_REPLACE_WITH='tuna'
-          export CARGO_REGISTRIES_TUNA_INDEX='https://mirrors.tuna.tsinghua.edu.cn/git/crates.io-index.git'
-          # --- 结束 ---
+          ID=`git rev-parse --abbrev-ref HEAD | grep -oP 'ch\K[0-_]'`
+
+          # 直接将环境变量作为 make 命令的前缀，以保证最高优先级
+          cd ci-user && \
+          CARGO_SOURCE_CRATES_IO_REPLACE_WITH='tuna' \
+          CARGO_REGISTRIES_TUNA_INDEX='https://mirrors.tuna.tsinghua.edu.cn/git/crates.io-index.git' \
+          make test CHAPTER=$ID passwd=${{ secrets.BASE_TEST_TOKEN }} > ../output.txt
 
-          ID=`git rev-parse --abbrev-ref HEAD | grep -oP 'ch\K[0-9]'`
-          cd ci-user && make test CHAPTER=$ID passwd=${{ secrets.BASE_TEST_TOKEN }} > ../output.txt
           cat ../output.txt
 
       - name: end