When I use GN to build Chromium, I get a mix of directory permissions in the "out" directory: Some 0755 (the default on my system) and some 0700.
I think what's happening is that if Ninja created the directory, then it has the default permissions. (Likewise if the tools/gn/bootstrap/bootstrap.py script created the directory.)
If GN created the directory it has 0700 permissions.
Previously when I built with GYP, all directories had the default permissions.
This is easy to fix after the fact, but it's annoying. (For a while I was confused why my Chromium build ran, but couldn't locate its debugging symbols.)

gn-dev thread: https://groups.google.com/a/chromium.org/d/msg/gn-dev/Xz4G3EBaNhU/uMLoqllaGQAJ