meson: Flush stdout in testwrap

Otherwise the progress won't reliably be displayed during a test.

Reviewed-by: Noah Misch 
Discussion: https://postgr.es/m/kx6xu7suexal5vwsxpy7ybgkcznx6hgywbuhkr6qabcwxjqax2@i4pcpk75jvaa
Backpatch-through: 16

diff --git a/src/tools/testwrap b/src/tools/testwrap
index 8ae8fb79ba7099de712c05f4d8138dc39bd185d8..21105146c9d6956cb677bce4564a27d66867f745 100755 (executable)
--- a/src/tools/testwrap
+++ b/src/tools/testwrap
@@ -61,6 +61,7 @@ for line in sp.stdout:
     if line.startswith(b'ok '):
         line = line.replace(b' # TODO ', b' # testwrap-overridden-TODO ', 1)
     sys.stdout.buffer.write(line)
+    sys.stdout.flush()
 returncode = sp.wait()
 
 if returncode == 0: