ncurses: avoid hardcoded assumptions about the layout of .OBJDIR

Abstract out the details of the FreeBSD build into a $TINFO_OBJDIR that
external builds can override if they orchestrate the build a bit
differently and have a different objdir layout as a result.  This makes
the ncurses build a little bit more flexible without requiring weird
backflips.

Reviewed by:	bapt, sjg
Sponsored by:	NetApp, Inc.
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D41834

lib/ncurses/config.mk

@@ -6,6 +6,8 @@ NCURSES_MAJOR=	6
 NCURSES_MINOR=	2
 NCURSES_PATCH=	20210220
 
+TINFO_OBJDIR?=	${.OBJDIR:H}/tinfo
+
 CFLAGS+=	-D_XOPEN_SOURCE_EXTENDED
 NCURSES_CFG_H=	${.CURDIR}/ncurses_cfg.h
 
@@ -17,7 +19,7 @@ CFLAGS+=	-I${.CURDIR:H}/ncurses
 
 CFLAGS+=	-I${NCURSES_DIR}/include
 CFLAGS+=	-I${NCURSES_DIR}/ncurses
-CFLAGS+=	-I${.OBJDIR:H}/tinfo/
+CFLAGS+=	-I${TINFO_OBJDIR}
 
 CFLAGS+=	-Wall
 
@@ -27,7 +29,7 @@ CFLAGS+=	-DHAVE_CONFIG_H
 
 # everyone needs this
 .PATH:		${NCURSES_DIR}/include
-.PATH:		${.OBJDIR:H}/tinfo/
+.PATH:		${TINFO_OBJDIR}
 
 # tools and directories
 AWK?=		awk

lib/ncurses/ncurses/Makefile

@@ -180,9 +180,9 @@ libncursesw.ald: ${.CURDIR}/${STATIC_LDSCRIPT}
 	    -e 's,@@STATICLIB_SUFFIX@@,${_STATICLIB_SUFFIX},g' \
 	    ${.ALLSRC} > ${.TARGET}
 
-lib_gen.c: MKlib_gen.sh ${.OBJDIR:H}/tinfo/curses.h ncurses_dll.h
+lib_gen.c: MKlib_gen.sh ${TINFO_OBJDIR}/curses.h ncurses_dll.h
 	LC_ALL=C sh ${NCURSES_DIR}/ncurses/base/MKlib_gen.sh "${CPP:N${CCACHE_BIN}} ${CFLAGS}" \
-	       "${AWK}" generated < ${.OBJDIR:H}/tinfo/curses.h >$@
+	       "${AWK}" generated < ${TINFO_OBJDIR}/curses.h >$@
 
 expanded.c: MKexpanded.sh
 	sh ${NCURSES_DIR}/ncurses/tty/MKexpanded.sh "${CC:N${CCACHE_BIN}} -E" ${CFLAGS} >expanded.c