Symptom
clang: warning: argument unused during compilation: '–gcc-toolchain=C:/Users/username/AppData/Local/Huawei/Sdk/openharmony/9/native/llvm' [-Wunused-command-line-argument];
The clang compiler in API version 9 reports a warning for each file compiled. Though the warnings can be suppressed with the -Wno-unused-command-line-argument option, manually adding the option can be troublesome if there are many files in the project.
Solution
The warnings are triggered by the -Werror and -Wunused-command-line-argument options in clang. They are likely caused by unsupported variable syntax in the code. To disable this specific type of warning, add the -Wno-unused-command-line-argument option to your configuration, or upgrade the SDK to API version 11.