[llvm] [LLVM][CMake] Build examples for llvm-test-depends (PR #171998)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

To check my understand of what this is going to do, does this sound correct?

 * `LLVM_INCLUDE_EXAMPLES=OFF`: Examples not built (and targets not generated).
 * `LLVM_INCLUDE_EXAMPLES=ON`, `LLVM_BUILD_EXAMPLES=OFF`: Examples not built by default target, but built by `check-llvm`. Examples not installed.
 * `LLVM_INCLUDE_EXAMPLES=ON`, `LLVM_BUILD_EXAMPLES=ON`: Examples built by default target and installed by install taret.

https://github.com/llvm/llvm-project/pull/171998