What is BuildOptions Flag for Use Prebuilt Engine (WebGL Dev Only Buildable With asm/this flag)

After upgrading to 2018.2.3, we noticed our webgl dev builds were failing with output below. Only way to build successfully was to switch to asm linking and turn on Use Prebuilt Engine / Dev flags in Build settings....
However, we need our command line Jenkins builder to be able to handle that if we need it to. I don't see this opion in BuildOptions class (I do see a BuildOptions.Development). Am I missing it?

Failed running "C:\Program Files\Unity 2018.2.3\Editor\Data\PlaybackEngines\WebGLSupport\BuildTools\Emscripten_Win\python\2.7.5.3_64bit\python.exe" "C:\Program Files\Unity 2018.2.3\Editor\Data\PlaybackEngines\WebGLSupport\BuildTools\Emscripten\emcc" @"C:\Users\username\source\repos\ares-game-client-ng\Assets\..\Temp\emcc_arguments.resp"
stdout:
stderr:WARNING:root:--separate-asm works best when compiling to HTML. Otherwise, you must yourself load the '.asm.js' file that is emitted separately, and must do so before loading the main '.js' file. [-Wseparate-asm]warning: unexpected number of arguments 2 in call to '_ZN6il2cpp6icalls8mscorlib6System6String22RedirectToCreateStringEv', should be 0warning: unexpected number of arguments 4 in call to