Fix make error in regression tests coming from midi2ly (issue 5777053)

[dak]

http://codereview.appspot.com/5777053/diff/1/make/midi-rules.make
File make/midi-rules.make (right):

http://codereview.appspot.com/5777053/diff/1/make/midi-rules.make#newcode12
make/midi-rules.make:12: (echo '\header {'; for f in $(HEADER_FIELDS);
do echo $$f'="'; cat $(outdir)/$*.$$f; echo '"'; done; echo '}') >
$(outdir)/$*.header
This won't do since it starts generated header strings with a newline
that does not belong there (I am surprised that your shell had a version
of echo not understanding -n).

You can try
... echo $$f'="'"`cat $(outdir)/$*.$$f`"'"'; done ...

That is a bit of quoting overkill.  It will probably do to write
... echo $$f="\"`cat $(outdir)/$*.$$f`\""; done

http://codereview.appspot.com/5777053/