mtest2make: hide output of successful tests

The softfloat tests are quite noisy; before the Meson conversion
they buffered the output in a file and emitted the output only
if the test failed.  Tweak mtest2make.py so that the courtesy
is extended to all non-TAP tests.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/test-driver.py

@@ -0,0 +1,35 @@
+#! /usr/bin/env python3
+
+# Wrapper for tests that hides the output if they succeed.
+# Used by "make check"
+#
+# Copyright (C) 2020 Red Hat, Inc.
+#
+# Author: Paolo Bonzini <pbonzini@redhat.com>
+
+import subprocess
+import sys
+import os
+import argparse
+
+parser = argparse.ArgumentParser(description='Test driver for QEMU')
+parser.add_argument('-C', metavar='DIR', dest='dir', default='.',
+                    help='change to DIR before doing anything else')
+parser.add_argument('-v', '--verbose', dest='verbose', action='store_true',
+                    help='be more verbose')
+parser.add_argument('test_args', nargs=argparse.REMAINDER)
+
+args = parser.parse_args()
+os.chdir(args.dir)
+
+test_args = args.test_args
+if test_args[0] == '--':
+    test_args = test_args[1:]
+
+if args.verbose:
+    result = subprocess.run(test_args, stdout=None, stderr=None)
+else:
+    result = subprocess.run(test_args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+    if result.returncode:
+        sys.stdout.buffer.write(result.stdout)
+sys.exit(result.returncode)