[clang-repl] Build and install clang-repl by default

[v.g.vassilev]

Summary

We have the basic infrastructure in place. We can recover from simple errors (recovering from errors in template instantiations is not yet supported). It looks like we are in a reasonably functional state for llvm13.

[teemperor]

I think my concerns from D96033 are all addressed by now, so this LGTM. Thanks!

[sylvestre.ledru]

Maybe add this to the release notes of clang 13 or 14?

clang/tools/clang-repl/CMakeLists.txt

 set( LLVM_LINK_COMPONENTS
   ${LLVM_TARGETS_TO_BUILD}
   Core
   Option
   OrcJIT
   Support
   )
 
 add_clang_executable(clang-repl
-  EXCLUDE_FROM_ALL
   ClangRepl.cpp
   )
 
 target_link_libraries(clang-repl PUBLIC
   clangBasic
   clangInterpreter
   clangTooling
   LLVMLineEditor
   )