Fix CMakeLists.txt

[xiaozhuai]

1. Add install target for minifb. Allow to use minifb by following.

find_package(minifb CONFIG REQUIRED)
add_executable(my_app main.cpp)
target_link_libraries(my_app PRIVATE minifb::minifb)

2. Remove msvc runtime library compile options, The CRT linkage should be specified by the user project, not the library.
3. Remove specify CMAKE_BUILD_TYPE. This should be specified by the user project.

[xiaozhuai]

Hello @emoon . Would you please review this pr? If it looks good for you, please merge.

[xiaozhuai]

@Darky-Lucera knock~ knock~

[Darky-Lucera]

Ok, I was looking at your changes and they make sense

Could you explain a little bit the last part?

install(TARGETS minifb EXPORT minifb)
file(GLOB_RECURSE HEADERS "${CMAKE_CURRENT_LIST_DIR}/include/*.h")
install(FILES ${HEADERS} DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
install(EXPORT minifb FILE minifb-config.cmake DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/minifb" NAMESPACE minifb::)

[xiaozhuai]

@Darky-Lucera Thank you for merging this pr.