diff -Nur qwt-6.1.5.old/qwtbuild.pri qwt-6.1.5/qwtbuild.pri

--- qwt-6.1.5.old/qwtbuild.pri	2020-06-01 20:48:07.321112118 +0400

+++ qwt-6.1.5/qwtbuild.pri	2020-09-19 01:05:19.842096481 +0400

@@ -14,7 +14,7 @@

 CONFIG           += qt

 CONFIG           += warn_on

 CONFIG           += no_keywords

-CONFIG           += silent

+#CONFIG           += silent

 DEFINES += QT_NO_DEPRECATED_WARNINGS # not fixing those before Qwt 6.2

diff -Nur qwt-6.1.5.old/qwtconfig.pri qwt-6.1.5/qwtconfig.pri

--- qwt-6.1.5.old/qwtconfig.pri	2020-06-01 20:48:07.325112226 +0400

+++ qwt-6.1.5/qwtconfig.pri	2020-09-19 01:10:47.546615714 +0400

@@ -19,7 +19,7 @@

 QWT_INSTALL_PREFIX = $$[QT_INSTALL_PREFIX]

 unix {

-    QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION

+    # QWT_INSTALL_PREFIX    = /usr/local/qwt-$$QWT_VERSION

     # QWT_INSTALL_PREFIX = /usr/local/qwt-$$QWT_VERSION-qt-$$QT_VERSION

 }

@@ -29,8 +29,8 @@

 }

 QWT_INSTALL_DOCS      = $${QWT_INSTALL_PREFIX}/doc

-QWT_INSTALL_HEADERS   = $${QWT_INSTALL_PREFIX}/include

-QWT_INSTALL_LIBS      = $${QWT_INSTALL_PREFIX}/lib

+QWT_INSTALL_HEADERS   = $$[QT_INSTALL_HEADERS]/qwt

+QWT_INSTALL_LIBS      = $$[QT_INSTALL_LIBS]

 ######################################################################

 # Designer plugin

@@ -42,7 +42,8 @@

 # runtime environment of designer/creator.

 ######################################################################

-QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer

+#QWT_INSTALL_PLUGINS   = $${QWT_INSTALL_PREFIX}/plugins/designer

+QWT_INSTALL_PLUGINS   = $$[QT_INSTALL_PLUGINS]/designer

 # linux distributors often organize the Qt installation

 # their way and QT_INSTALL_PREFIX doesn't offer a good

@@ -110,7 +111,7 @@

 # to your qmake project file.

 ######################################################################

-#QWT_CONFIG     += QwtMathML

+QWT_CONFIG     += QwtMathML

 ######################################################################

 # If you want to build the Qwt designer plugin,