How to call emmake to pass down MAKEFLAGS

I have a main Makefile that build a few Emscriptenized tools. Inside I call `emmake make`, but this does not pass down root MAKEFLAGS (parallel build), since `$(MAKE)` must be used. If I pass `MAKEFLAGS` explicitly, it creates some bogus `-j` makeflag if no MAKEFLAGS were actually passed to the main make.

Is there an accepted way of passing down MAKEFLAGS to submake? Should I use `emmake $(MAKE)`?

I can create my own SUBMAKEFLAGS - that should work, but it's a somewhat nasty hack.