cmake-gui: Restore search bar for cache view and environment dialog

This was broken by commit e42d2c5880 (cmake-gui: Support building
against Qt6, 2020-12-17, v3.20.0-rc1~205^2~7).

Fixes: #21850

Source/QtDialog/EnvironmentDialog.cxx

@@ -110,8 +110,14 @@ EnvironmentDialog::EnvironmentDialog(const QProcessEnvironment& environment,
                    &EnvironmentDialog::addEntry);
   QObject::connect(this->RemoveEntry, &QAbstractButton::clicked, this,
                    &EnvironmentDialog::removeSelectedEntries);
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 12, 0))
+  QObject::connect(this->Search, &QLineEdit::textChanged, this->m_filter,
+                   QOverload<const QString&>::of(
+                     &EnvironmentSearchFilter::setFilterRegularExpression));
+#else
   QObject::connect(this->Search, &QLineEdit::textChanged, this->m_filter,
                    &EnvironmentSearchFilter::setFilterFixedString);
+#endif
   QObject::connect(this->Environment->selectionModel(),
                    &QItemSelectionModel::selectionChanged, this,
                    &EnvironmentDialog::selectionChanged);

Source/QtDialog/QCMakeCacheView.cxx

@@ -170,7 +170,11 @@ bool QCMakeCacheView::showAdvanced() const
 
 void QCMakeCacheView::setSearchFilter(const QString& s)
 {
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 12, 0))
+  this->SearchFilter->setFilterRegularExpression(s);
+#else
   this->SearchFilter->setFilterFixedString(s);
+#endif
 }
 
 QCMakeCacheModel::QCMakeCacheModel(QObject* p)