diff -rupN --no-dereference qwt-6.1.4/textengines/mathml/mathml.pro qwt-6.1.4-new/textengines/mathml/mathml.pro
--- qwt-6.1.4/textengines/mathml/mathml.pro 2019-01-02 17:21:31.504466243 +0100
+++ qwt-6.1.4-new/textengines/mathml/mathml.pro 2020-01-06 17:17:19.695623736 +0100
@@ -60,6 +60,8 @@ contains(QWT_CONFIG, QwtPkgConfig) {
QMAKE_PKGCONFIG_LIBDIR = $${QWT_INSTALL_LIBS}
QMAKE_PKGCONFIG_INCDIR = $${QWT_INSTALL_HEADERS}
+
+ QMAKE_PKGCONFIG_DESTDIR = pkgconfig
# QMAKE_PKGCONFIG_DESTDIR is buggy, in combination
# with including pri files: better don't use it