llvm/clang/include/clang/CIR/CMakeLists.txt

set(MLIR_INCLUDE_DIR ${LLVM_MAIN_SRC_DIR}/../mlir/include ) # --includedir
set(MLIR_TABLEGEN_OUTPUT_DIR ${CMAKE_BINARY_DIR}/tools/mlir/include)
include_directories(${MLIR_INCLUDE_DIR})
include_directories(${MLIR_TABLEGEN_OUTPUT_DIR})

add_subdirectory(Dialect)