Umask ignored on Linux

UE4 is hardcoded to use 755 for files and directories. See mkdir() in Engine/Source/Runtime/Core/Private/Unix/UnixPlatformFile.cpp

This is also repeated for Android, HTML5, and Lumin but i cannot confirm any symptoms on those. In a Linux development environment it is useful for different users to share assets and DDC. 755 forces read only for everyone but the owner, making this difficult. A user should be able to change their umask to override this.

1. Change the umask from the default 022 to 002 and reload the profile
2. # echo "umask 002" > ~/.profile && source ~/.profile
3. Open the editor, create a blank project "MyProject", close the editor.
4. # ./UE4Editor
5. Check the permissions of the created directory and files
6. # ls -lR ~/Documents/Unreal\ Projects

Results: Directories and files were created with permissions rw-r-r-.

Expected: Directories and files should be created with permissions rw-rw-r--