ignore the `build` subdirectory
ignore the `build` subdirectory

produced by distutils

Signed-off-by: Daniel Halperin <1a02732a15f637c31107256cbee5819e36aa7c67@cs.washington.edu>

uwescience/raco,uwescience/raco,uwescience/raco,uwescience/raco,uwescience/raco