Ninja builds currently do not work when building in paths with spaces in them. We currently tell developers not to do this in our documentation, but it's a trap for newcomers and there's really no reason this should be the case. There are two problems that cause the behavior, and both should be corrected:

1. Ninja does not expand response files with spaces in the path. This may be a Ninja bug or some behavior related to how we generate build.ninja.
2. We do not escape or quote tool or file paths that may have spaces in them.