[PATCH v2 2/3] qapi: use env var to trigger qapi test output updates

["Daniel P. Berrangé" <berrange@redhat.com>]

It is possible to pass --update to tests/qapi-schema/test-qapi.py
to make it update the output files on error. This is inconvient
to achieve though when test-qapi.py is run indirectly by make/meson.

Instead simply allow for an env variable to be set:

 $ QAPI_TEST_UPDATE=1 make check-qapi-schema

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tests/qapi-schema/test-qapi.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/qapi-schema/test-qapi.py b/tests/qapi-schema/test-qapi.py
index 2160cef082..75f2759fd6 100755
--- a/tests/qapi-schema/test-qapi.py
+++ b/tests/qapi-schema/test-qapi.py
@@ -215,7 +215,8 @@ def main(argv):
         (dir_name, base_name) = os.path.split(t)
         dir_name = dir_name or args.dir
         test_name = os.path.splitext(base_name)[0]
-        status |= test_and_diff(test_name, dir_name, args.update)
+        update = args.update or "QAPI_TEST_UPDATE" in os.environ
+        status |= test_and_diff(test_name, dir_name, update)
 
     exit(status)
 
-- 
2.39.2