Re: Use $(MAKE) instead of 'make' in lilypond-book regtests (issue 569400043 by address@hidden)

[nine . fierce . ballads]

How does this interact with CPU_COUNT, which is documented in the
Contributor's Guide thus (emphasis mine)?

    The most time consuming task for building the documentation is
    running LilyPond to build images of music, and *** there cannot be
    several simultaneously running lilypond-book instances, *** so the
    -j make option does not significantly speed up the build
    process. To help speed it up, the makefile variable CPU_COUNT may
    be set in local.make or on the command line to the number of .ly
    files that LilyPond should process simultaneously, e.g. on a
    bi-processor or dual core machine:

        make -j3 CPU_COUNT=3 doc

This is how I always build.  Is it going to have the same effect now, or
will it do something new, e.g. attempt 9 concurrent jobs?

https://codereview.appspot.com/569400043/