warnings of non-verbose builds

There are warnings during a build that I would like to see fixed:

* Building lilypond with gcc 14.2.0, I get the following warning
  during the creation of the `lilypond` binary.

  ```
  lto-wrapper: warning: using serial compilation of 20 LTRANS jobs
  lto-wrapper: note: see the '-flto' option documentation for more information
  ```

  My knowledge of link optimization is zero; I assume that the warning
  is mainly informative, so I'm not really concerned.  However, it
  shows up during a non-verbose build (nicely coloured on the
  terminal), and I wonder how this could be properly suppressed — or
  maybe fixed, if there is something to fix...

* Compiling the Scheme files produces an awful lot of output, with a
  lot of (harmless?) warnings.  Again, it would be nice if someone™
  could stand up and make them disappear so that real problems in the
  Scheme code are not missed.

Takers?


    Werner