swrast: add correct include for out-of-tree builds

The xmlpool/options.h file was not accessible when building
out-of-tree leading to failure.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70378
Reported-by: Fabio Pedretti <fabio.ped@libero.it>
Tested-by: Fabio Pedretti <fabio.ped@libero.it>
Tested-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Andreas Boll <andreas.boll.dev@gmail.com>

src/gallium/targets/dri-swrast/Makefile.am

@@ -33,6 +33,7 @@ AM_CPPFLAGS = \
 	-I$(top_srcdir)/src/gallium/winsys \
 	-I$(top_srcdir)/src/mesa \
 	-I$(top_srcdir)/src/mapi \
+	-I$(top_builddir)/src/mesa/drivers/dri/common \
 	-DGALLIUM_RBUG \
 	-DGALLIUM_TRACE \
 	-DGALLIUM_SOFTPIPE \

src/mesa/drivers/dri/swrast/Makefile.am

@@ -30,6 +30,7 @@ AM_CFLAGS = \
 	-I$(top_srcdir)/src/mapi \
 	-I$(top_srcdir)/src/mesa/ \
 	-I$(top_srcdir)/src/mesa/drivers/dri/common \
+	-I$(top_builddir)/src/mesa/drivers/dri/common \
 	$(DEFINES) \
 	$(VISIBILITY_CFLAGS)