Skip tst_QFile::largeUncFileSupport

If more than one VM tries to run the test at the same time, it times out. These
sharing violations were attempted to be worked around in 1c3dc8c, but the
workaround just leads to timeout, not success.

Task-number: QTQAINFRA-1727
Task-number: QTBUG-66216
Change-Id: If8bfd60dbb6575843680971d45b1c82e5beff534
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Sami Nurmenniemi <sami.nurmenniemi@qt.io>

tests/auto/corelib/io/qfile/tst_qfile.cpp

@@ -1642,6 +1642,15 @@ static bool fOpen(const QByteArray &fileName, const char *mode, FILE **file)
 
 void tst_QFile::largeUncFileSupport()
 {
+    // Currently there is a single network test server that is used by all VMs running tests in
+    // the CI. This test accesses a file shared with Samba on that server. Unfortunately many
+    // clients accessing the file at the same time is a sharing violation. This test already
+    // attempted to deal with the problem with retries, but that has led to the test timing out,
+    // not eventually succeeding. Due to the timeouts blacklisting the test wouldn't help.
+    // See https://bugreports.qt.io/browse/QTQAINFRA-1727 which will be resolved by the new
+    // test server architecture where the server is no longer shared.
+    QSKIP("Multiple instances of running this test at the same time fail due to QTQAINFRA-1727");
+
     qint64 size = Q_INT64_C(8589934592);
     qint64 dataOffset = Q_INT64_C(8589914592);
     QByteArray knownData("LargeFile content at offset 8589914592");