Only attempt to build the HTML version of the man page if xsltproc is installed.

configure.ac

@@ -447,10 +447,17 @@ fi
 # Look for xmltoman
 AC_CHECK_PROGS([XMLTOMAN], [xmltoman])
 if test -z "$XMLTOMAN"; then
-  AC_MSG_WARN([xmltoman not found - not rebuilding man pages])
+  AC_MSG_WARN([xmltoman not found - not installing man page])
 fi
 AM_CONDITIONAL([HAVE_XMLTOMAN], [test -n "$XMLTOMAN"])
 
+# Look for xmltoman
+AC_CHECK_PROGS([XSLTPROC], [xsltproc])
+if test -z "$XSLTPROC"; then
+  AC_MSG_WARN([xsltproc not found - not creating html version of man])
+fi
+AM_CONDITIONAL([HAVE_XSLTPROC], [test -n "$XSLTPROC"])
+
 # Checks for header files.
 AC_CHECK_HEADERS([getopt_long.h])
 AC_CHECK_HEADERS([arpa/inet.h fcntl.h limits.h mach/mach.h memory.h netdb.h netinet/in.h stdint.h stdlib.h string.h sys/ioctl.h sys/socket.h sys/time.h syslog.h unistd.h])

man/Makefile.am

@@ -1,10 +1,12 @@
 man_MANS = shairport-sync.7
 
 if HAVE_XMLTOMAN
-all-local: shairport-sync.html
-
 shairport-sync.7: shairport-sync.7.xml
 	xmltoman $< > $@
+endif
+
+if HAVE_XSLTPROC
+all-local: shairport-sync.html
 
 shairport-sync.html: xmltoman.xsl shairport-sync.7.xml 
 	xsltproc  $^ > $@