I had a fair amount of trouble building from source. The issues were simple (and obvious in retrospect) but they need to be mentioned.
Included in the Sigil archive are the source for two libraries, tidyLib and ZipArchive. If you just follow the instructions on the wiki, your make will fail when it tries to link these libraries. Each must be built separately using the same instructions as the wiki tells you for the main program, but they do not have a "make install" target. You must hand copy the created libraries (libtidyLib.a and libZipArchive.a) to /usr/lib. I tried sending them to /usr/local/lib, but it didn't help. Last, build Sigil according to the instructions and it should build fine.
I'm not reall happy about having to put them in the main library directory (I'd have preferred /usr/local) but this seems to work.