ncurses: serialize the tinfo build a little bit

Move ncurses_dll.h to GENHDRS to start with; it's been generated from
ncurses_dll.h.in for years, so it's not actually in a different category
than all of the other GENHDRS.  Slap an .ORDER on it to ensure that we
build ncurses_dll.h and curses.h before any *.c gets compiled.

This should sufficiently address a build race seen downstream where
ncurses_dll.h is present but not yet populated.

Reviewed by:	bapt
Sponsored by:	NetApp, Inc.
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D43540

lib/ncurses/tinfo/Makefile

@@ -74,6 +74,7 @@ GENHDRS=	\
 	hashsize.h \
 	init_keytry.h \
 	ncurses_def.h \
+	ncurses_dll.h \
 	nomacros.h \
 	parametrized.h \
 	term.h \
@@ -170,9 +171,8 @@ CWARNFLAGS.comp_parse.c= ${NO_WUNUSED_BUT_SET_VARIABLE}
 CWARNFLAGS.read_entry.c= ${NO_WUNUSED_BUT_SET_VARIABLE}
 
 # Installed
-HEADERS=	curses.h term.h termcap.h unctrl.h
-SRCHDRS=	ncurses_dll.h
-CLEANFILES+=	ncurses_dll.h
+HEADERS=	curses.h ncurses_dll.h term.h termcap.h unctrl.h
+SRCHDRS=
 
 INCS=		${HEADERS} ${SRCHDRS}
 INCSLINKS=	curses.h ${INCLUDEDIR}/ncurses.h
@@ -214,6 +214,14 @@ FILESGROUPS=	DOCS
 # Generated source
 .ORDER: names.c codes.c
 
+# Serialize the build just a little bit; there's nothing stopping the build from
+# proceeding before ncurses_dll.h and curses.h are actually generated on a clean
+# build since we have no dependency information to prevent it.
+.ORDER: ncurses_dll.h curses.h
+.for f in ${SRCS:M*.c}
+.ORDER: curses.h ${f}
+.endfor
+
 names.c: MKnames.awk
 	${AWK} -f ${NCURSES_DIR}/ncurses/tinfo/MKnames.awk bigstrings=${USE_BIG_STRINGS} ${NCURSES_DIR}/include/Caps > names.c