building with "CLANG"

[other at ahhyes.net]

Hi Guys,

I recently tried to give CLANG a go with rebuilding the system 
(9.0-RELEASE to 9.1-RELEASE). Having read: 
https://wiki.freebsd.org/BuildingFreeBSDWithClang everything seems to be 
working ok.

I noticed something in the document that got me concerned:

# Don't forget this when using Jails!
NO_FSCHG=

There is a suggestion to add the above to src.conf -- Can someone 
please explain what this does? Having forgotten to do this, am I going 
to have any major problems?

Alex.