LilyPond 2.21.80 installer on MacOS 10.15

[Hans Åberg]

MacOS 11 is about to be released, so this is a LilyPond 2.21.80 installer, 
latest unstable release, for use on MacOS 10.15. As it will take some time to 
get MacPorts working on Mac OS 11, and this installer likely will not work on 
it, the best shot is to install this on MacOS 10.15 and then upgrade.

The installer is made from MacPorts lilypond-devel, available on the link below 
[1]. It installs in /opt/lilypond/, with the program in 
/opt/lilypond/bin/lilypond.

If you have already something installed in this directory, it may be prudent to 
remove it first. This can be done by the command
sudo rm -rf /opt/lilypond

1. https://web2.storegate.com/share/wiM8LyF

It may be the case that 'lilypond' is best to be run from a script that sets 
LC_CTYPE=en_US.UTF-8 (which otherwise on MacOS is LC_CTYPE=UTF-8). It can be 
created and installed as follows:

In Terminal write (^D is <control>D):
% cat > lilypond
export LC_CTYPE=en_US.UTF-8
export LANG=en_US.UTF-8
exec /opt/lilypond/bin/lilypond "$@“
^D

% chmod a+x lilypond
% sudo -s cp lilypond /usr/local/bin/lilypond

The program can then be called by 'lilypond' in Terminal, as /usr/local/bin/ is 
in the program searchpath.

And do 'rm lilypond' if you do not want to keep the local copy of the script.