In Non-Project Mode, you must read each file individually before executing the compilation commands.
The example script below shows how to use one or more XDC files for synthesis and implementation.
Example Script:
read_verilog [glob src/*.v]
read_xdc wave_gen_timing.xdc
read_xdc wave_gen_pins.xdc
synth_design -top wave_gen -part xc7k325tffg900-2
opt_design
place_design
route_design