sna: Keep @NOWARNFLAGS@ last

As the last option overrides the earlier options, make sure these
particular overrides always take effect by adding them last.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/Makefile.am

@@ -22,7 +22,6 @@ SUBDIRS = brw fb
 
 AM_CFLAGS = \
 	@CWARNFLAGS@ \
-	@NOWARNFLAGS@ \
 	-I$(top_srcdir)/src \
 	-I$(top_srcdir)/src/render_program \
 	$(XORG_CFLAGS) \
@@ -135,3 +134,5 @@ git_version.h: $(top_srcdir)/.git/HEAD $(shell sed -e '/ref:/!d' -e 's#ref: *#$(
 	@V=`git describe`; echo "static const char git_version[] = \"$$V\";" > git_version.h
 sna_driver.c: git_version.h
 endif
+
+AM_CFLAGS += @NOWARNFLAGS@

src/sna/brw/Makefile.am

@@ -29,7 +29,6 @@ AM_CFLAGS = \
 	@XORG_CFLAGS@ \
 	@UDEV_CFLAGS@ \
 	@DRM_CFLAGS@ \
-	@NOWARNFLAGS@ \
 	$(NULL)
 
 if DEBUG
@@ -58,3 +57,5 @@ brw_test_SOURCES = \
 brw_test_LDADD = \
 	libbrw.la \
 	$(NULL)
+
+AM_CFLAGS += @NOWARNFLAGS@