Help: Add notes for topic 'makefile-progress-improvements'

Help/release/dev/makefile-progress-improvements.rst

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+makefile-progress-improvements
+------------------------------
+
+* With Makefile generators, the build-time progress output has been improved.
+  It no longer mixes progress and build rule messages during parallel builds.
+  The link rule messages now have progress and are displayed as bold green
+  instead of bold red (since red is often associated with an error message).