QtAutogen: Process 'rcc --list' stdout and stderr separately (#15523)

The stderr may have warning messages.  We should not treat these lines
as resource files.  However, we must still recognize error message lines
for missing resource files that may be generated.

Extend the QtAutogen test to cover a generated resource as the only one
listed in a .qrc file.  This causes 'rcc --list' to print a warning to
stderr that we now intend to ignore.

1 files changed, 1 insertions, 0 deletions

diff --git a/Tests/QtAutogen/generated.txt.in b/Tests/QtAutogen/generated.txt.in
new file mode 100644
index 0000000..77507bb
--- /dev/null
+++ b/Tests/QtAutogen/generated.txt.in
@@ -0,0 +1 @@
+Some generated text file.