Build library as part of another product without conflicts

[AndreyAlifanov]

We need to build clickhouse-cpp as part of our product.
But CMakeLists.txt uses global options, sush as BUILD_SHARED_LIBS, BUILD_TESTS and so on.
This breaks our build system.

So I made changes in CMakeLists.txt.
If clickhouse-cpp is built as part of another product, global options are not changed by clickhouse-cpp.

Usage example. In this example flags touch only clickhouse-cpp, and don't affect our projects.

#outer CMakeLists.txt file
set (BUILD_SHARED_LIBS OFF)
set (BUILD_BENCHMARK OFF)
set (BUILD_TESTS OFF)
add_subdirectory(clickhouse-cpp)

[CLAassistant]

All committers have signed the CLA.

[Enmk]

I believe you need to have a corresponding option declaration clause (OPTION(CHCPP_EMBEDDED_BUILD ...)) before this if just to explain intention and simplify user's life.

[Enmk]

Also, please consider changing option name to CLICKHOUSE_CPP_EMBEDDED_BUILD, like we have in 3.0: https://github.com/ClickHouse/clickhouse-cpp/blob/3.0/CMakeLists.txt

[AndreyAlifanov]

Thank you for answers and pieces of advice. I found another solution. It is not visible to user and handled automatically by build system.
I think, it will be better than new option.