Is your feature request related to a problem? Please describe.

CMake configuration does not support disabling libsystemd dependency. This may lead to incompatibility between builds from systemd and non-systemd environments when the use of libsystemd is not explicitly required. The code supports the HAVE_LIBSYSTEMD macro, which is automatically detected if building with libsystemd is possible. It is necessary to add the ability to explicitly disable building with this dependency when it is not required.

Describe the solution you'd like

Add CMake option GRPC_USE_LIBSYSTEMD=ON/OFF or even ON/OFF/FORCE_ON (the latter will force-require libsystemd).