cmake updates desired

[JaeseungYeom]

I am including gotcha in my project via cmake FetchContent method. I found there were a couple of changed needed for me to make it work.

1. sed -i "s/CMAKE_SOURCE_DIR/CMAKE_CURRENT_SOURCE_DIR/g" CMakeLists.txt
2. sed -i "s|PATH_VARS gotcha_INSTALL_INCLUDE_DIR PATH_VARS gotcha_INSTALL_LIBRARY_DIR|PATH_VARS gotcha_INSTALL_INCLUDE_DIR gotcha_INSTALL_LIBRARY_DIR|g" CMakeLists.txt
3. sed -i "s|add_subdirectory(example)||g" src/CMakeLists.txt

1 is used in favor of FetchContent
2 was a necessary fix
3 was a necessary get-around. Something was failing, and I could not find any way to disable building example.