The result of $(wildcard *) is random.
Sort input files to reduce build-compare noise.

---
 docs/Makefile |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: xen-4.18.0-testing/docs/Makefile
===================================================================
--- xen-4.18.0-testing.orig/docs/Makefile
+++ xen-4.18.0-testing/docs/Makefile
@@ -192,7 +192,7 @@ uninstall: uninstall-man-pages uninstall
 
 # Individual file build targets
 html/index.html: $(DOC_HTML) $(CURDIR)/gen-html-index INDEX
-	$(PERL) -w -- $(CURDIR)/gen-html-index -i INDEX html $(DOC_HTML)
+	$(PERL) -w -- $(CURDIR)/gen-html-index -i INDEX html $(sort $(DOC_HTML))
 
 html/%.txt: %.txt
 	@$(INSTALL_DIR) $(@D)
@@ -207,8 +207,8 @@ html/hypercall/%/index.html: $(CURDIR)/x
 	$(INSTALL_DIR) $(@D)
 	$(PERL) -w $(CURDIR)/xen-headers -O $(@D) \
 		-T 'arch-$* - Xen public headers' \
-		$(patsubst %,-X arch-%,$(filter-out $*,$(DOC_ARCHES))) \
-		$(patsubst %,-X xen-%,$(filter-out $*,$(DOC_ARCHES))) \
+		$(sort $(patsubst %,-X arch-%,$(filter-out $*,$(DOC_ARCHES)))) \
+		$(sort $(patsubst %,-X xen-%,$(filter-out $*,$(DOC_ARCHES)))) \
 		$(EXTRA_EXCLUDE) \
 		$(XEN_ROOT)/xen include/public include/xen/errno.h