harness: Pass executable directory to wlcs server
This allows mir to start.
This currently only passes the first argument as mir will complain if there are unrecognised arguments and I can't see a way to carve out unhandled arguments to be passed from libtest-mimic
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CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER='gdb --args' WSSY_LIB=/usr/lib64/mir/miral_wlcs_integration.so cargo test --test wayassay