It sounds like you're compiling from the git repository, not just installing. There are Ubuntu packages available from the Julia downloads page if you'd prefer:
http://julialang.org/downloads/See also:
https://github.com/JuliaLang/julia#ubuntuAnd elsewhere in the readme, under "ncurses build error":
"Install the
libncurses5 development package
- Debian/Ubuntu:
apt-get install libncurses5-dev"
Finally, the build process is just make, so nothing will rebuild unless it has to when you run make again. If you install that package and run make again, it should finish pretty quickly.