Merge pull request SCons#4515 from mwichmann/doc/variables2

Update docs for Variables

Author: bdbaddog

CHANGES.txt

@@ -40,6 +40,7 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
       build pdf versions which are then ignored.
     - Add the ability to print a Variables object for debugging purposes
       (provides a __str__ method in the class).
+    - Update manpage and user guide for Variables usage.
 
 
 RELEASE 4.7.0 -  Sun, 17 Mar 2024 17:22:20 -0700

RELEASE.txt

@@ -63,6 +63,7 @@ DOCUMENTATION
 
 - Updated Value Node docs.
 - Update manpage for Tools, and for the TOOL variable.
+- Update manpage and user guide for Variables usage.