Potential issue with `add_ldflags` not being picked up

[xdoardo]

I added multiple calls to add_ldflags(...) in cheriot-rtos/tests/xmake.lua, which are not picked up.
It seems that this line sets up the call to ld: could it be that it ignores the calls to the function mentioned above?

A possible MRE: add

	add_ldflags("-lnonexistent")

under

firmware("test-suite")

in cheriot-rtos/tests/xmake.lua, which should give an error for a library not found, but does not.