Install cargo-llvm-cov only if needed

Author: EFanZh

.github/workflows/ci.yml

@@ -42,6 +42,7 @@ jobs:
         steps:
           - uses: actions/checkout@v4
           - run: rustup update
+          - run: rustup component add llvm-tools
           - run: cargo install cargo-llvm-cov
           - run: cargo llvm-cov --lcov --workspace --output-path lcov.info
           - uses: codecov/codecov-action@v5

rust-toolchain.toml

@@ -1,3 +1,2 @@
 [toolchain]
 channel = "stable"
-components = ["llvm-tools"]