print/lilypond: Add build option to use Guile2

PR:	254572
Submitted by:	m.ne@gmx.net (maintainer)

print/lilypond/Makefile

@@ -25,7 +25,6 @@ BUILD_DEPENDS=	bash:shells/bash \
 LIB_DEPENDS=	libfontconfig.so:x11-fonts/fontconfig \
 		libfreetype.so:print/freetype2 \
 		libgmp.so:math/gmp \
-		libguile.so:lang/guile1 \
 		libltdl.so:devel/libltdl
 RUN_DEPENDS=	${LOCALBASE}/share/fonts/dejavu/DejaVuSans-Bold.ttf:x11-fonts/dejavu \
 		mftrace:print/mftrace
@@ -61,11 +60,16 @@ INFO=		lilypond-changes \
 				music-glossary
 PLIST_SUB=	DISTVERSION=${DISTVERSION}
 
-OPTIONS_DEFINE=	URW NLS
+OPTIONS_DEFINE=	GUILE2 NLS URW
 OPTIONS_SUB=	yes
 
+GUILE2_DESC=	Use guile2 (will incur some performance penalty)
 URW_DESC=	Use bundled URW fonts
 
+GUILE2_LIB_DEPENDS=	libgc-threaded.so:devel/boehm-gc-threaded \
+			libguile-2.2.so:lang/guile2
+GUILE2_LIB_DEPENDS_OFF=	libguile.so:lang/guile1
+
 NLS_USES=	gettext
 
 URW_BUILD_DEPENDS=	urw-core35-fonts>0:x11-fonts/urw-core35-fonts