Choose specific options based on the value of firrtlOptions.compilerName.

[ucbjrl]

(from @seldridge freechipsproject/firrtl#916) freechipsproject/chisel-testers#214 makes sense, generally. The user should be able to add options. However, I think there's motivation for verilogToCpp or verilogToVerilator to choose specific options based on the value of firrtlOptions.compilerName. I.e., if the user has requested -X sverilog it would be reasonable to include -sv when calling Verilator automatically.

Note: once the options/annotations stuff lands, the clean way to do this is to examine the contents of the EmitterAnnotation.