tests: build the helper program by default

Usually we may configure and make, then goto ./tests/qemu-iotest,
check. In this case an error will happen since helper program
was not built. This patch simply build it by default. A better way
may be introducing Makefile in ./tests/qemu-iotest, but it is more
complicate to handle out of tree case, and a bit overkill
for a single file now, we can do that when more files come.
Signed-off-by: NWenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/Makefile

@@ -252,8 +252,10 @@ check-report.html: check-report.xml
 
 # Other tests
 
+QEMU_IOTESTS_HELPERS-$(CONFIG_LINUX) = tests/qemu-iotests/socket_scm_helper$(EXESUF)
+
 .PHONY: check-tests/qemu-iotests-quick.sh
-check-tests/qemu-iotests-quick.sh: tests/qemu-iotests-quick.sh qemu-img$(EXESUF) qemu-io$(EXESUF) tests/qemu-iotests/socket_scm_helper$(EXESUF)
+check-tests/qemu-iotests-quick.sh: tests/qemu-iotests-quick.sh qemu-img$(EXESUF) qemu-io$(EXESUF) $(QEMU_IOTESTS_HELPERS-y)
 	$<
 
 .PHONY: check-tests/test-qapi.py
@@ -275,5 +277,9 @@ check-unit: $(patsubst %,check-%, $(check-unit-y))
 check-block: $(patsubst %,check-%, $(check-block-y))
 check: check-qapi-schema check-unit check-qtest
 
+# Build the help program automatically
+
+all: $(QEMU_IOTESTS_HELPERS-y)
+
 -include $(wildcard tests/*.d)
 -include $(wildcard tests/libqos/*.d)