clang-format generated code for easier debugging

cf/Makefile.am.common

@@ -143,11 +143,20 @@ check-local::
 
 SUFFIXES += .x .z .hx
 
+# It's useful for debugging to format generated sources.  The default for all
+# clang-format styles is to sort includes, but in many cases in-tree we really
+# don't want to do that.
 .x.c:
-	@cmp -s $< $@ 2> /dev/null || cp $< $@
+	@if [ -z "$(CLANG_FORMAT)" ]; then \
+	    cmp -s $< $@ 2> /dev/null || cp $< $@; \
+	else \
+	    cp $< $@.tmp.c; \
+            $(CLANG_FORMAT) -style='{BasedOnStyle: Chromium, SortIncludes: false}' -i $@.tmp.c; \
+	    cmp -s $@.tmp.c $@ 2> /dev/null || mv $@.tmp.c $@; \
+	fi
 
 .hx.h:
-	@cmp -s $< $@ 2> /dev/null || cp $< $@
+	@cmp -s $< $@ 2> /dev/null || cp $< $@;
 
 SUFFIXES += .1 .3 .5 .7 .8 .cat1 .cat3 .cat5 .cat7 .cat8