LLVM utilities

### Comment:

Hi I'm in the process of swapping out a from-source LLVM build with the llvmdev packages.

utilities (count, not, FileCheck etc) end up in a non default location [here](https://github.com/conda-forge/llvmdev-feedstock/blob/main/recipe/build.sh#L47) and that's caused some problems for us particularly with the cmake function `add_lit_testsuite` where FileCheck for example is a dependency that cannot otherwise be found. What's the rational with the current design?

Start with the linked recipe/build.sh location around line 47 and inspect how LLVM utilities such as FileCheck are installed. Then review CMake's add_lit_testsuite expectations; done means the current utility placement and the resulting discoverability problem have a documented resolution.

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