lib/virtual_oss: don't (over)link to libsamplerate

These plugins require samplerate.h due to virtual_oss's int.h including
it, but don't use any symbols directly so don't link to the library.

Centralize adding the include path.

Reviewed by:	christos
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D54705

lib/virtual_oss/Makefile.inc

@@ -3,5 +3,7 @@ PACKAGE=	sound
 SHLIBDIR=	${LIBDIR}/virtual_oss
 
 CFLAGS+=	-I${SRCTOP}/usr.sbin/virtual_oss/virtual_oss
+# XXX virtual_oss/int.h includes samplerate.h, but the library isn't used
+CFLAGS+=	-I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/private/samplerate
 
 .include "../Makefile.inc"

lib/virtual_oss/bt/Makefile

@@ -4,8 +4,7 @@ SRCS=		bt.c \
 		avdtp.c \
 		sbc_encode.c
 
-CFLAGS+= 	-I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/private/samplerate
-LIBADD=		bluetooth samplerate sdp
+LIBADD=		bluetooth sdp
 
 .if defined(HAVE_LIBAV)
 CFLAGS+=	-I${LOCALBASE:U/usr/local}/include -DHAVE_LIBAV

lib/virtual_oss/null/Makefile

@@ -2,7 +2,4 @@ SHLIB_NAME= 	voss_null.so
 
 SRCS=		null.c
 
-CFLAGS+= 	-I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/private/samplerate
-LIBADD=		samplerate
-
 .include <bsd.lib.mk>

lib/virtual_oss/oss/Makefile

@@ -2,7 +2,4 @@ SHLIB_NAME= 	voss_oss.so
 
 SRCS=		oss.c
 
-CFLAGS+= 	-I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/private/samplerate
-LIBADD=		samplerate
-
 .include <bsd.lib.mk>

lib/virtual_oss/sndio/Makefile

@@ -2,9 +2,7 @@ SHLIB_NAME= 	voss_sndio.so
 
 SRCS=		sndio.c
 
-CFLAGS+= 	-I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/private/samplerate \
-		-I${LOCALBASE:U/usr/local}/include
+CFLAGS+=	-I${LOCALBASE:U/usr/local}/include \
 LDFLAGS+=	-L${LOCALBASE:U/usr/local}/lib -lsndio
-LIBADD=		samplerate
 
 .include <bsd.lib.mk>