Unless the Xilinx libraries are pre-compiled (not the case in the full version of the tools) you need to run the library compilation script Xilinx provides.
Also
mkdir work is unlikely to be the way you create a library in ncvhdl, simulators usually require you use some specific library creation command to do this, e.g.
vlib work for Modelsim.
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Here
this might help you set things up properly to compile your design.
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And
here is an AR on compiling Vivado libraries in NCsim.