Since sigil-0.5.x some patches were accepted (from
https://bugzilla.redhat.com/show_bug.cgi?id=772362) to enable building with system libs; so you can try building with your system-provided boost libs, start anew (or run 'make clean'), then delete ( or rename) src/BoostParts in the sigil source directory and make sure boost-devel is installed on your system, then try again.