lang/sbcl: Utilize SBCL_HOME to build custom core file and set it to empty.

Reported by:	Catherine Tower <catherine__at__towernetdotdev>

(cherry picked from commit 888bfec23a)

lang/sbcl/Makefile

@@ -5,6 +5,7 @@
 PORTNAME=	sbcl
 DISTVERSION=	2.1.9
 DISTVERSIONSUFFIX=	-source
+PORTREVISION=	1
 PORTEPOCH=	1
 CATEGORIES=	lang lisp
 MASTER_SITES=	SF/${PORTNAME}/${PORTNAME}/${DISTVERSION} \
@@ -143,6 +144,7 @@ do-install:
 	MAN_DIR="${STAGEDIR}${MANPREFIX}/man" \
 	INFO_DIR="${STAGEDIR}${PREFIX}/${INFO_PATH}" \
 	DOC_DIR="${STAGEDIR}${DOCSDIR}" \
+	SBCL_HOME="" \
 	${SH} install.sh)
 .for M in ${CONMODULES}
 	${MKDIR} ${STAGEDIR}${PREFIX}/lib/${PORTNAME}/${M}