[web/staticcontrollers] create a unique temporary file for concat handling Predictable names means different processes can race against each other. Let's avoid that and use mkstemp to get a real unique temporary file, and atomically rename it when we're done. Closes #3524182

include *.py
include */*.py
recursive-include data *.gif *.png *.ico *.css *.js
recursive-include i18n *.po
recursive-include wdoc *