[Scons-users] "no dependency generated" when warnings are turned on

[Mats Wichmann]

So turning on the dependency warning setting, got lots (10,000 according
to a grep of a suddenly huge build log) of warnings of the form

scons: warning: No dependency generated for file: blah (included from:
source file in the tree)

after a quick sampling, these all look like they are files external to
the project, specifically system headers.

I'm presuming this is just ignorable, and perhaps the reason why
dependency warnings are off by default?

or does this indicate something dubious in the project setup?