ยง How to link against MLIR with CMake

Since MLIR hasn't setup the nice tooling that LLVM has around CMake as far as I can tell, one needs to actually know CMake to link against MLIR. However, as is well known, CMake incantations are handed down by preists who spend the better part of their lives studying the tome that is the CMake manual. I, an unlucky soul had to go on this adventure, and I hope to spare you the trouble. I wished to link against a static library build of MLIR. The secret lies in the find_library call: 
#If the variable has been set by -DMLIR_INCLUDE_PATH, then keep it.
#Otherwise fallback to the environment variable $MLIR_INCLUDE_PATH.
#if neither, then *shrug*.
IF(NOT MLIR_INCLUDE_PATH)
    set (MLIR_INCLUDE_PATH $ENV{MLIR_INCLUDE_PATH})
endif()

#Resolve for:
#- a library target called `MLIRAnalysis`
#- asking to link against `libMLIAnalysis.a`
#- using the variable MLIR_INCLUDE_PATH which as we saw before
##  is either an environment variable or a cmake option
target_include_directories(languagemodels PRIVATE ${MLIR_INCLUDE_PATH})
I cribbed the actual things to link against from the path mlir/examples/Toy/Ch2/CMakeLists.txt which helpfully lists MLIR things it needs to link against. The full CMakeLists is here: 
cmake_minimum_required(VERSION 3.5)
project(languagemodels)

set(CMAKE_CXX_STANDARD 14)

## I don't want to use find_package since I want proper control over where my LLVM comes from.
## find_package(LLVM REQUIRED)

add_executable(languagemodels
        rnn.cpp codegenc.h lang.h codegenmlir.h)

## Attempt to take these as command line arguments. IF that fails,
## lookup environment.
IF(NOT MLIR_INCLUDE_PATH)
    set (MLIR_INCLUDE_PATH $ENV{MLIR_INCLUDE_PATH})
endif()

IF(NOT MLIR_LIBRARY_PATH)
    set (MLIR_LIBRARY_PATH $ENV{MLIR_LIBRARY_PATH})
endif()

target_include_directories(languagemodels PRIVATE ${MLIR_INCLUDE_PATH})
find_library(MLIRAnalysis MLIRAnalysis ${MLIR_LIBRARY_PATH})
find_library(MLIRIR MLIRIR ${MLIR_LIBRARY_PATH})
find_library(MLIRParser MLIRParser ${MLIR_LIBRARY_PATH})
find_library(MLIRSideEffects MLIRSideEffects ${MLIR_LIBRARY_PATH})
find_library(MLIRTransforms MLIRTransforms ${MLIR_LIBRARY_PATH})
find_library(LLVMCore LLVMCore ${MLIR_LIBRARY_PATH})
find_library(LLVMSupport LLVMSupport ${MLIR_LIBRARY_PATH})

## debugging to check if it's been set properly
message(MLIR_INCLUDE_PATH ${MLIR_INCLUDE_PATH})
message(MLIR_LIBRARY_PATH ${MLIR_LIBRARY_PATH})
message(MLIRAnalysis ${MLIRAnalysis})

target_link_libraries(languagemodels
        ${MLIRAnalysis}
        ${MLIRIR}
        ${MLIRParser}
        ${MLIRSideEffects}
        ${MLIRTransforms}
        ${LLVMCore}
        ${LLVMSupport})