MWDT: linker: fix regresion

Fixes commit 5badbfe2 ("cmake: move
toolchain_ld_baremetal to linker properties.") which broke build for
ARC MWDT toolchain.

Fixes failure:
```
lldac: error: cannot open ,--orphan-handling=warn: No such file or
  directory
ninja: build stopped: subcommand failed.
```

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>