Suppress gcc warning -Wmemset-elt-size on test code

The test uses a 64-unit array and deliberately clears various portions
of it, provoking a gcc warning:

 warning: ‘memset’ used with length equal to number of elements without multiplication by element size [-Wmemset-elt-size]

The calls to memset() do, in fact, have a sizeof(T) factor in their
size. Suppress this warning for the duration of that test.

Change-Id: I7d144d655a75f5ef4449fa3b956f80bcc509a83b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

tests/auto/corelib/global/qtendian/tst_qtendian.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the test suite of the Qt Toolkit.
@@ -156,6 +156,9 @@ void tst_QtEndian::fromLittleEndian()
 
 #undef ENDIAN_TEST
 
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_GCC("-Wmemset-elt-size")
+
 template <typename T>
 void transformRegion_template(T (*transformOne)(T), void (*transformRegion)(const void *, qsizetype, void *))
 {
@@ -225,6 +228,7 @@ void transformRegion_template(T (*transformOne)(T), void (*transformRegion)(cons
     for (int i = 0; i < 64; ++i)
         QCOMPARE(dest[i], expected);
 }
+QT_WARNING_POP
 
 void tst_QtEndian::fromBigEndianRegion_data()
 {