cross compile dll on mac OSX with cmake and mingw - c++

Question

I installed the bwapi via wine on Mac OSX. And I try to compile the ExampleAIModule in it with CMake and MinGW on Mac OSX. The ExampleAIModule is actually a VS2017 project, I write a CMakeLists.txt, ran cmake CMakeLists.txt && make VERBOSE=1 got some errors. I want to know how to fix my CMakeLists.txt?
The folder structure:
BWAPI/ExampleAIModule/CMakeLists.txt
BWAPI/ExampleAIModule/Source/*.cpp *.h
BWAPI/include/*.h
BWAPI/lib/BWAPI.lib
BWAPI/lib/BWAPIClient.lib
make got errors:
Linking CXX shared library libExampleAIModule.dylib
/usr/local/Cellar/cmake/3.2.2/bin/cmake -E cmake_link_script CMakeFiles/ExampleAIModule.dir/link.txt --verbose=1
i686-w64-mingw32-g++ -std=c++11 -O3 -DNDEBUG -dynamiclib -Wl,-headerpad_max_install_names -o libExampleAIModule.dylib -install_name #rpath/libExampleAIModule.dylib CMakeFiles/ExampleAIModule.dir/Source/Dll.cpp.o CMakeFiles/ExampleAIModule.dir/Source/ExampleAIModule.cpp.o -L/.wine/drive_c/Starcraft/BWAPI/ExampleAIModule/../lib
i686-w64-mingw32-g++: error: rpath/libExampleAIModule.dylib: No such file or directory
i686-w64-mingw32-g++: error: unrecognized command line option ‘-install_name’
make[2]: *** [libExampleAIModule.dylib] Error 1
make[1]: *** [CMakeFiles/ExampleAIModule.dir/all] Error 2
CMakeLists.txt
cmake_minimum_required(VERSION 3.0.0 FATAL_ERROR)
################### Variables. ####################
# Change if you want modify path or other values. #
###################################################
set(PROJECT_NAME ExampleAIModule)
# Output Variables
# Folders files
set(CPP_DIR_1 Source)
set(HEADER_DIR_1 Source)
############## Define Project. ###############
# ---- This the main options of project ---- #
##############################################
project(${PROJECT_NAME} CXX)
# Define Release by default.
if(NOT CMAKE_BUILD_TYPE)
set(CMAKE_BUILD_TYPE "Release")
message(STATUS "Build type not specified: defaulting to release.")
endif(NOT CMAKE_BUILD_TYPE)
# Definition of Macros
add_definitions(
-DNOMINMAX
-D_DEBUG
-D_WINDOWS
-D_USRDLL
-DEXAMPLEAIMODULE_EXPORTS
-DUNICODE
-D_UNICODE
)
################# Flags ################
# Defines Flags for Windows and Linux. #
########################################
if(MSVC)
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /W3 /EHsc")
set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /W3 /EHsc")
endif(MSVC)
if(NOT MSVC)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
endif()
endif(NOT MSVC)
########### Add by me #############
SET(CMAKE_C_COMPILER i686-w64-mingw32-gcc)
SET(CMAKE_CXX_COMPILER i686-w64-mingw32-g++)
include_directories(../include)
link_directories(../lib)
################ Files ################
# -- Add files to project. -- #
#######################################
file(GLOB SRC_FILES
${CPP_DIR_1}/*.cpp
${HEADER_DIR_1}/*.h
)
# Add library to build.
add_library(${PROJECT_NAME} SHARED
${SRC_FILES}
)

Answer 1

CMake always use toolchains to compile for a specific platform/target, as mentioned here. However, for cross-compilation, you need to specify the toolchain file it needs to use. This is done using the CMAKE_TOOLCHAIN_FILE variable, as explained here.
The parameters related to the compilation (such as the system name, processor, compiler, etc.) on the target platform shouldn't be in the CMakeLists.txt file where you defined your project (using the project function).
Instead, you're supposed to set the compilers and other parameters related to cross-compilation in a toolchain file. And you may have a toolchain file for each platform you like to cross-compile for.
This is how your toolchain file may look like, assuming that the compilers are in the path:
set(CMAKE_SYSTEM_NAME Windows)
set(CMAKE_SYSTEM_PROCESSOR x86_64)
SET(CMAKE_C_COMPILER i686-w64-mingw32-gcc)
SET(CMAKE_CXX_COMPILER i686-w64-mingw32-g++)
If your toolchain file has the path /toolchains/windows.cmake, you need to pass -DCMAKE_TOOLCHAIN_FILE=/toolchains/windows.cmake to cmake.
This design keeps your project's CMakeLists.txt file toolchain-agnostic.