test-includes: Build a library instead of a binary

We need to build the .o's, but don't need to link. Build a static
library instead of a binary to accmoplish this. This removes the need to
have all the libc and crt stuff built, which is required for a
binary. In addition, trying to build a non-standard binary runs into
trouble with undefined symbols on arm related to EABI, even when using a
simplified startup with -nostdlib -e start.

Turn back on testing includes, now that it works.

Sponsored by:		Netflix
Reviewed by:		brooks, markj (prior version)
Differential Revision:	https://reviews.freebsd.org/D33452

Makefile.inc1

@@ -1128,6 +1128,7 @@ _includes:
 .if !empty(SUBDIR_OVERRIDE) && make(buildworld)
 	${_+_}cd ${.CURDIR}; ${WMAKE} MK_INCLUDES=yes SHARED=symlinks includes
 .endif
+	${_+_}cd ${.CURDIR};  ${WMAKE} test-includes
 _libraries:
 	@echo
 	@echo "--------------------------------------------------------------"

tools/build/test-includes/Makefile

@@ -13,11 +13,11 @@
 # programs to detect FreeBSD has different headers, omitting internal
 # headers cuts down on the noise w/o causing problems for the goal.
 #
-PROG=	test-includes
-SRCS=	test-includes.c
-INTERNALPROG=	This is a compile-only test
+LIB=	test-includes
+INTERNALLIB=	This is a compile-only test
 MAN=
 HDRS!=	(cd ${SRCTOP}/sys; ls sys/[^_]*.h net*/[^_]*.h)
+NO_PIC=	yes
 
 # Some files have to be clean for extra defines too...
 CFLAGS.event.c=	-D_WANT_KEVENT32 -D_WANT_FREEBSD11_KEVENT
@@ -33,6 +33,8 @@ ${h:R}.c:
 .endif
 .endfor
 
+test-includes: lib${LIB}.a .PHONY
+
 #
 # Target to make the current known bad list. In general, this list should only
 # ever shrink and never grow.
@@ -49,4 +51,4 @@ badfiles.inc:
 	done;									\
 	echo) > ${.CURDIR}/badfiles.inc
 
-.include <bsd.prog.mk>
+.include <bsd.lib.mk>

tools/build/test-includes/test-includes.c

@@ -1,7 +0,0 @@
-/* Public domain */
-
-int
-main(void)
-{
-	return 0;
-}