Many LLDB's dotest.py based tests require the `make` tool. If it's not found in Path, they fail with an obscure error and show up as `UNRESOLVED`. On Windows, llvm-lit takes care of MSYS based testing tools like cat, printf, etc., but `make` is not part of that. Let's catch the situation early and check for it at configuration time.
This error isn't fatal: It should fail the build, but not immediately stop the configuration process. There might be other issues further down the line that can be caught in the same buildbot run.
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