Only run xmlto once

Signed-off-by: Tim Waugh <[email protected]>

Author: twaugh

Makefile.am

@@ -35,7 +35,9 @@ man_MANS = doc/interdiff.1 doc/filterdiff.1 doc/fixcvsdiff.1 doc/rediff.1 \
 	doc/grepdiff.1 doc/recountdiff.1 doc/unwrapdiff.1 doc/dehtmldiff.1 \
 	doc/flipdiff.1 doc/espdiff.1 doc/patchview.1
 
-$(man_MANS): doc/patchutils.xml
+$(man_MANS): _MANPAGES
+
+_MANPAGES: doc/patchutils.xml
 	$(XMLTO) man -o doc $<
 endif