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Jon MeowandChandler Carruth
f58e5da827
Per chandlerc's comment: First, this builds inside the Bazel tree rather than in the source repository. This ensures we start in a clean directory each time the repository rule is run again. We don't need to detect an existing build with this, and it will only be rebuilt when the workspace file or the repository rule implementation is changed. This can be forced by using: ``` bazel sync --configure ``` Second, we use an implicit dependency on the `WORKSPACE` file to locate the workspace directory automatically, and the `HEAD` file from the `llvm-project` submodule to trigger a rebuild if the submodule is updated. Third, teach the CMake script to try to use a system-installed `clang` if installed and not overridden by the `CC` environment variable. This is very different from the prior logic -- this is only used with the CMake build, and so should work with any system C++ compiler that can build Clang and LLVM. Lastly, this tweaks the CMake options to tune this build given that we now fully control it and it will only be used in this context. This still results in a 1.5gb build for me. =/ But its as small as I can make it really. It's a frustrating long list, but I couldn't find a more brief way of representing this. Co-authored-by: Chandler Carruth <chandlerc@gmail.com>