Add plusargs support to testbench.cc
Add plusargs support to testbench.cc

Signed-off-by: Claire Wolf <da7dd17269675e6648b2de3690262d0e18b89cca@symbioticeda.com>

cliffordwolf/picorv32,cliffordwolf/picorv32,cliffordwolf/picorv32,cliffordwolf/picorv32