Update coverage.yml

.buildkite/coverage.yml

@@ -17,5 +17,5 @@ steps:
           - BOOST_ROOT=/root/opt/boost_1_66_0
           - OPENSSL_ROOT_DIR=/usr/include/openssl
           - WASM_ROOT=/root/opt/wasm
-          - LLVMCOV_PATH=/root/opt/wasm/bin/llvm-cov
+          - PATH=/root/opt/wasm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
     timeout: 30