tst_QSaveFile: skip test that fails when run as root

FAIL!  : tst_QSaveFile::retryTransactionalWrite() '!file.open(QIODevice::WriteOnly)' returned FALSE. ()
   Loc: [/home/tjmaciei/src/qt/qt5/qtbase/tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp(156)]

strace reveals:
access("/TEMPDIR/outfile.ro", W_OK) = 0

Change-Id: Ibdc95e9af7bd456a94ecfffd1603eb371aadb02b
Reviewed-by: David Faure <david.faure@kdab.com>

tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp

@@ -136,6 +136,10 @@ void tst_QSaveFile::retryTransactionalWrite()
 {
 #ifndef Q_OS_UNIX
     QSKIP("This test is Unix only");
+#else
+    // root can open the read-only file for writing...
+    if (geteuid() == 0)
+        QSKIP("This test does not work as the root user");
 #endif
     QTemporaryDir dir;
     QVERIFY2(dir.isValid(), qPrintable(dir.errorString()));