Short fix:
You need backticks (`) for the --build option: --build=`...`.
Explanation:
The --host option tells the configure script which platform you are
building *for*. The --build option tells your configure script which
platform you are building *on*.
What the backticks do is to replace everything inside `...` with the
output of the command build-aux/config.guess. This command guesses your
platform.
You can omit the --build option, in which case the configure script
will just guess your platform (by calling build-aux/config.guess
itself). This usually works, but sometimes gives a warning.
Martin