cmake: Add support for on-demand local trace output

Alex Turbovrequested to merge
zaufi/cmake:bug/19416 into master

Add a CMAKE_TRACE variable that can be set to enable output for a region of a script as if the --trace or --trace-expand options were given on the command line.

Fixes: #19416
Topic-rename: trace-variables

Edited by Brad King

Merge request reports