Our cross-builds build against Qt 5.10.x or lower and were broken by D7524. This diff fixes that and
[00:44:34][Step 1/1] ../../src/qt/guiutil.cpp: In function ‘qreal GUIUtil::calculateIdealFontSize(int, const QString&, QFont, qreal, qreal)’:
[00:44:34][Step 1/1] ../../src/qt/guiutil.cpp:957:16: error: ‘class QFontMetrics’ has no member named ‘horizontalAdvance’
[00:44:34][Step 1/1] if (fm.horizontalAdvance(text) < width) {
[00:44:34][Step 1/1] ^~~~~~~~~~~~~~~~~
This diff fixes that without an additional preprocessor conditional block