docker: allow running from srcdir != builddir build

The new script uses "git submodule", which is picky about being invoked
from the top of the git checkout.  Invoke the script from $(SRC_PATH)
to avoid git's wrath.

Fixes: b7f404201e45e99da23b9764dec27ce5f965cdcd
Cc: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Message-Id: <1508331989-142364-1-git-send-email-pbonzini@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
diff --git a/tests/docker/Makefile.include b/tests/docker/Makefile.include
index 38874ec..02cd520 100644
--- a/tests/docker/Makefile.include
+++ b/tests/docker/Makefile.include
@@ -18,11 +18,11 @@
 IMAGES ?= %
 
 CUR_TIME := $(shell date +%Y-%m-%d-%H.%M.%S.$$$$)
-DOCKER_SRC_COPY := docker-src.$(CUR_TIME)
+DOCKER_SRC_COPY := $(BUILD_DIR)/docker-src.$(CUR_TIME)
 
 $(DOCKER_SRC_COPY):
 	@mkdir $@
-	$(call quiet-command, $(SRC_PATH)/scripts/archive-source.sh $@/qemu.tar, \
+	$(call quiet-command, cd $(SRC_PATH) && scripts/archive-source.sh $@/qemu.tar, \
 		"GEN", "$@/qemu.tar")
 	$(call quiet-command, cp $(SRC_PATH)/tests/docker/run $@/run, \
 		"COPY","RUNNER")