builder scanners don't process on Value nodes

[dragon512]

Builders are not applying scanners to value nodes

A sample can be found at https://github.com/dragon512/scons-issues/tree/master/value_scan

the root directory has a PipFile to help with quick setup of a python environment with SCons in it

[dragon512]

Just adding a note that you wanted another example that might show a use case of the Value node being used in a builder. The current point just shows the technical result that a Value is not scanned. I will make another example of a possible use case that could be done. I will add a link once I get a few cycles...