gnu: lilypond: Use texlive-union.

* gnu/packages/music.scm (lilypond)[arguments]: Add phase "use-texlive-union".
[native-inputs]: Replace "texlive" with a texlive-union.

gnu/packages/music.scm

@@ -652,6 +652,15 @@ (define-public lilypond
                             "/share/fonts/opentype/"))
        #:phases
        (modify-phases %standard-phases
+         (add-after 'unpack 'use-texlive-union
+           (lambda _
+             ;; FIXME: fonts are not found and have to be generated in HOME.
+             (setenv "HOME" "/tmp")
+             ;; The test for the "lh" package fails, even though it is among
+             ;; the inputs.
+             (substitute* "configure"
+               (("TEX_FIKPARM=.*") "TEX_FIKPARM=found\n"))
+             #t))
          (add-after 'unpack 'fix-path-references
           (lambda _
             (substitute* "scm/backend-library.scm"
@@ -693,7 +702,10 @@ (define-public lilypond
        ("gettext" ,gettext-minimal)
        ("imagemagick" ,imagemagick)
        ("netpbm" ,netpbm) ;for pngtopnm
-       ("texlive" ,texlive) ;metafont and metapost
+       ("texlive" ,(texlive-union (list texlive-metapost
+                                        texlive-generic-epsf
+                                        texlive-latex-lh
+                                        texlive-latex-cyrillic)))
        ("texinfo" ,texinfo)
        ("texi2html" ,texi2html)
        ("rsync" ,rsync)