Set MANUFACTURER env variable when running wixl

The MANUFACTURER env variable is mandatory since it is used
in the data files. wixl will exit with parser error if it
is not set

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

data/Makefile.am

@@ -1,5 +1,6 @@
 NULL =
 CLEANFILES =
+MANUFACTURER = Virt Manager Project
 
 EXTRA_DIST =					\
 	spice-xpi-client-remote-viewer		\
@@ -29,7 +30,7 @@ virt-viewer-$(WIXL_ARCH)-$(VERSION).msi: virt-viewer.wxs deps.txt
 	find $$DESTDIR | wixl-heat -p $$DESTDIR$(prefix)/		\
 	    --component-group CG.virt-viewer --var var.DESTDIR		\
 	    --directory-ref=INSTALLDIR > virt-viewer-files.wxs &&	\
-	wixl -D SourceDir=$(prefix)					\
+	MANUFACTURER="$(MANUFACTURER)" wixl -D SourceDir=$(prefix)	\
              -D DESTDIR=$$DESTDIR$(prefix)				\
              --arch $(WIXL_ARCH)					\
              -o $@							\