I have poppler-0.24.3 installed with the jpeg use flag, but /usr/include/poppler/goo/JpegWriter.h is missing. Reproducible: Always app-text/poppler-0.24.3 was built with the following: USE="cairo cxx introspection jpeg lcms png qt4 tiff utils -cjk -curl -debug -doc -jpeg2k"
It seems that JpegWriter.h is installed if I enable the jpeg2k flag, but I don't see why that should be necessary.