You'll need the following dependencies:

• glib-2.0
• gobject-2.0
• granite >=0.5
• gtk+-3.0
• libecal-1.2
• libedataserver-1.2
• libical
• meson
• valac

Run meson build to configure the build environment. Change to the build directory and run ninja to build

meson build --prefix=/usr
cd build
ninja

To install, use ninja install, then execute with io.elementary.tasks

ninja install
io.elementary.tasks