cmake : update to 3.19 (#351)

- update from 3.0 (from 2014) to 3.19 (from 2020)
- move some global setting onto the targets (through a cmake include)

examples/talk.wasm/CMakeLists.txt

@@ -9,6 +9,8 @@ add_executable(${TARGET}
     gpt-2.cpp
     )
 
+include(DefaultTargetOptions)
+
 target_link_libraries(${TARGET} PRIVATE
     whisper
     )