Source: https://src.fedoraproject.org/rpms/qwt/blob/rawhide/f/qwt-pkgconfig.patch

--- a/src/src.pro
+++ b/src/src.pro
@@ -86,14 +86,14 @@ contains(QWT_CONFIG, QwtPkgConfig) {
     greaterThan(QT_MAJOR_VERSION, 4) {
 
         QMAKE_PKGCONFIG_FILE = Qt$${QT_MAJOR_VERSION}$${QMAKE_PKGCONFIG_NAME}
-        QMAKE_PKGCONFIG_REQUIRES = Qt5Widgets Qt5Concurrent Qt5PrintSupport
+        QMAKE_PKGCONFIG_REQUIRES = Qt$${QT_MAJOR_VERSION}Widgets Qt$${QT_MAJOR_VERSION}Concurrent Qt$${QT_MAJOR_VERSION}PrintSupport
 
         contains(QWT_CONFIG, QwtSvg) {
-            QMAKE_PKGCONFIG_REQUIRES += Qt5Svg
+            QMAKE_PKGCONFIG_REQUIRES += Qt$${QT_MAJOR_VERSION}Svg
         }
 
         contains(QWT_CONFIG, QwtOpenGL) {
-            QMAKE_PKGCONFIG_REQUIRES += Qt5OpenGL
+            QMAKE_PKGCONFIG_REQUIRES += Qt$${QT_MAJOR_VERSION}OpenGL
         }
 
         QMAKE_DISTCLEAN += $${DESTDIR}/$${QMAKE_PKGCONFIG_DESTDIR}/$${QMAKE_PKGCONFIG_FILE}.pc