You'll need the following dependencies:

• gobject-introspection
• libecal1.2-dev
• libedataserver1.2-dev
• libical-dev
• libgranite-dev
• libwingpanel-2.0-dev
• meson
• valac >= 0.40.3

Run meson to configure the build environment and then ninja to build

meson build --prefix=/usr
cd build
ninja

To install, use ninja install

sudo ninja install