cmake: use add_compile_options() to pass compile options

cmake: use add_compile_options() to pass compile options

add_definitions() is for adding "-D" define flags, while "-include" does
not define flags, so let's be explicit and use add_compile_options()
instead.

this change partially reverts 5fb90bb79671b8e22f507728e4b4b948a591f98f.
back then, we were using ubuntu bionic for building windows packages.
but since we've switched to ubuntu focal, where cmake 3.16 is available,
there is no reason to stick with add_definitions() anymore.

Signed-off-by: Kefu Chai <kchai@redhat.com>