Modify optimisation flags for various functions.
This fixes non-determinism issues in the asm produced for
these function when cross-compiling on x86_64 and aarch64 for
the arm64-apple-darwin HOST.

--- a/qtbase/src/corelib/itemmodels/qitemselectionmodel.cpp
+++ b/qtbase/src/corelib/itemmodels/qitemselectionmodel.cpp
@@ -1078,9 +1078,9 @@ void QItemSelectionModelPrivate::_q_layoutChanged(const QList<QPersistentModelIn
 
     if (hint != QAbstractItemModel::VerticalSortHint) {
         // sort the "new" selection, as preparation for merging
-        std::stable_sort(savedPersistentIndexes.begin(), savedPersistentIndexes.end(),
+        std::sort(savedPersistentIndexes.begin(), savedPersistentIndexes.end(),
                          qt_PersistentModelIndexLessThan);
-        std::stable_sort(savedPersistentCurrentIndexes.begin(), savedPersistentCurrentIndexes.end(),
+        std::sort(savedPersistentCurrentIndexes.begin(), savedPersistentCurrentIndexes.end(),
                          qt_PersistentModelIndexLessThan);
 
         // update the selection by merging the individual indexes
@@ -1092,8 +1092,8 @@ void QItemSelectionModelPrivate::_q_layoutChanged(const QList<QPersistentModelIn
         savedPersistentCurrentIndexes.clear();
     } else {
         // sort the "new" selection, as preparation for merging
-        std::stable_sort(savedPersistentRowLengths.begin(), savedPersistentRowLengths.end());
-        std::stable_sort(savedPersistentCurrentRowLengths.begin(), savedPersistentCurrentRowLengths.end());
+        std::sort(savedPersistentRowLengths.begin(), savedPersistentRowLengths.end());
+        std::sort(savedPersistentCurrentRowLengths.begin(), savedPersistentCurrentRowLengths.end());
 
         // update the selection by merging the individual indexes
         ranges = mergeRowLengths(savedPersistentRowLengths);

--- a/qtbase/src/corelib/itemmodels/qitemselectionmodel_p.h
+++ b/qtbase/src/corelib/itemmodels/qitemselectionmodel_p.h
@@ -76,7 +76,7 @@ public:
     void _q_rowsAboutToBeInserted(const QModelIndex &parent, int start, int end);
     void _q_columnsAboutToBeInserted(const QModelIndex &parent, int start, int end);
     void _q_layoutAboutToBeChanged(const QList<QPersistentModelIndex> &parents = QList<QPersistentModelIndex>(), QAbstractItemModel::LayoutChangeHint hint = QAbstractItemModel::NoLayoutChangeHint);
-    void _q_layoutChanged(const QList<QPersistentModelIndex> &parents = QList<QPersistentModelIndex>(), QAbstractItemModel::LayoutChangeHint hint = QAbstractItemModel::NoLayoutChangeHint);
+    __attribute__ ((optnone)) void _q_layoutChanged(const QList<QPersistentModelIndex> &parents = QList<QPersistentModelIndex>(), QAbstractItemModel::LayoutChangeHint hint = QAbstractItemModel::NoLayoutChangeHint);
 
     inline void remove(QList<QItemSelectionRange> &r)
     {

--- a/qtbase/src/corelib/time/qdatetimeparser_p.h
+++ b/qtbase/src/corelib/time/qdatetimeparser_p.h
@@ -215,7 +215,7 @@ private:
             : value(ok == Invalid ? -1 : val), used(read), zeroes(zs), state(ok)
             {}
     };
-    ParsedSection parseSection(const QDateTime &currentValue, int sectionIndex,
+    __attribute__ ((optnone)) ParsedSection parseSection(const QDateTime &currentValue, int sectionIndex,
                                int offset, QString *text) const;
     int findMonth(const QString &str1, int monthstart, int sectionIndex,
                   int year, QString *monthName = nullptr, int *used = nullptr) const;

--- a/qtbase/src/corelib/time/qtimezoneprivate_p.h
+++ b/qtbase/src/corelib/time/qtimezoneprivate_p.h
@@ -191,7 +191,7 @@ public:
     virtual ~QUtcTimeZonePrivate();
 
     // Fall-back for UTC[+-]\d+(:\d+){,2} IDs.
-    static qint64 offsetFromUtcString(const QByteArray &id);
+    static __attribute__ ((optnone)) qint64 offsetFromUtcString(const QByteArray &id);
 
     QUtcTimeZonePrivate *clone() const override;
 
--- a/qtbase/src/widgets/widgets/qcalendarwidget.cpp
+++ b/qtbase/src/widgets/widgets/qcalendarwidget.cpp
@@ -329,13 +329,13 @@ class QCalendarYearValidator : public QCalendarDateSectionValidator
 
 public:
     QCalendarYearValidator();
-    virtual Section handleKey(int key) override;
+    __attribute__ ((optnone)) virtual Section handleKey(int key) override;
     virtual QDate applyToDate(QDate date, QCalendar cal) const override;
     virtual void setDate(QDate date, QCalendar cal) override;
     virtual QString text() const override;
     virtual QString text(QDate date, QCalendar cal, int repeat) const override;
 private:
-    int pow10(int n);
+    __attribute__ ((optnone)) int pow10(int n);
     int m_pos;
     int m_year;
     int m_oldYear;