It appears the current stable version of inkscape fails to build due to an incomplete resolution of bug # 655130: checking for freetype-config... no configure: error: Cannot find freetype-config Reproducible: Always
What version of media-libs/freetype do you have installed? Where's your "emerge --info" output?
I have exactly the same problem. The version of the package freetype - 2.9.1-r4. The problem was solved by rolling back to version 2.9
You could simply stop mixing stable inkscape package with unstable freetype package. stable =media-libs/freetype-2.9.1-r3 works perfectly fine with stable inkscape and the only difference to =media-libs/freetype-2.9.1-r4 is that -r3 still ships the deprecated "freetype-config" script.