docs: fix ability to view web pages from build tree

Some of the web content is only present in the source tree, thus when
viewing pages from the build tree they appear missing.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

docs/Makefile.am

@@ -39,6 +39,30 @@ modules_admin = libvirt-admin
 modules_qemu = libvirt-qemu
 modules_lxc = libvirt-lxc
 
+all: vpathhack
+
+# This hack enables us to view the web pages
+# from within the uninstalled build tree
+vpathhack:
+	@for dir in fonts js logos; \
+	do \
+	  test -e $$dir || ln -s $(srcdir)/$$dir $$dir ; \
+	done
+	@for file in $(css); \
+	do \
+	  test -e $$file || ln -s $(srcdir)/$$file $$file ; \
+	done
+
+clean-local:
+	for dir in fonts js logos; \
+	do \
+	  rm -f $$dir ; \
+	done
+	for file in $(css); \
+	do \
+	  rm -f $$file ; \
+	done
+
 apihtml = \
   html/index.html \
   $(apihtml_generated)