qapi: Pass '-u' when doing non-silent diff

Ed-script diffs are awful compared to context diffs.  Fix another
'diff -q' while in the area (if the files are different, being
noisy makes it easier to diagnose why).

While at it, diff .err before .out, because if a test fails, .err
is more likely to contain the most important information for
fixing the failure.

Fixes: 46ec4fc
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180315125116.804342-1-eblake@redhat.com>

tests/Makefile.include

@@ -929,14 +929,14 @@ $(patsubst %, check-%, $(check-qapi-schema-y)): check-%.json: $(SRC_PATH)/%.json
 		$^ >$*.test.out 2>$*.test.err; \
 		echo $$? >$*.test.exit, \
 		"TEST","$*.out")
-	@diff $(SRC_PATH)/$*.out $*.test.out
 	@# Sanitize error messages (make them independent of build directory)
-	@perl -p -e 's|\Q$(SRC_PATH)\E/||g' $*.test.err | diff $(SRC_PATH)/$*.err -
-	@diff $(SRC_PATH)/$*.exit $*.test.exit
+	@perl -p -e 's|\Q$(SRC_PATH)\E/||g' $*.test.err | diff -u $(SRC_PATH)/$*.err -
+	@diff -u $(SRC_PATH)/$*.out $*.test.out
+	@diff -u $(SRC_PATH)/$*.exit $*.test.exit
 
 .PHONY: check-tests/qapi-schema/doc-good.texi
 check-tests/qapi-schema/doc-good.texi: tests/qapi-schema/doc-good.test.texi
-	@diff -q $(SRC_PATH)/tests/qapi-schema/doc-good.texi $<
+	@diff -u $(SRC_PATH)/tests/qapi-schema/doc-good.texi $<
 
 .PHONY: check-decodetree
 check-decodetree: