To match JPEG colors you need not dcraw.c color profiles, but profiles used by camera vendors for in-camera processing (unavailable in most cases).

Also, the main problem is to repeat vendor's tone/contrast curve (which, in turn, changes when photographer change camera contrast/saturation/color mode) to match midtone brightness and highlights compression.

So, if your target is 'embedded JPEG match', than you (very likely) need own RAW postprocessing code instead of LibRaw::dcraw_process()