toolchain: arcmwdt: override unsuitable default implementations

Provide toolchain-specific implementations for the new functions
added in d77b58aa, because the default ones end up with build failures.

As the MWDT toolchain doesn't support different combinations of
compilers and linkers, there's no need to pass any linker properties
from the compiler, at least for the time being. Moreover, the default
implementation of compiler_set_linker_properties() uses the compiler
flag (--print-libgcc-file-name) that doesn't make any sense for MWDT.
Therefore, provide an empty implementation of the function.

The default implementation of toolchain_linker_add_compiler_options()
doesn't cause any issues for now, but it's still better to replace
it with the passthrough implementation borrowed from ld/lld.

Signed-off-by: Ilya Tagunov <Ilya.Tagunov@synopsys.com>