qwt-qt5: Fix multilib install

| ERROR: qwt-qt5-6.1.3-r0 do_package: QA Issue: qwt-qt5: Files/directories were installed but not shipped in any package:
|   /usr/lib/libqwt.so.6
|   /usr/lib/libqwt.so.6.1
|   /usr/lib/libqwt.so
|   /usr/lib/libqwt.so.6.1.3
|   /usr/lib/pkgconfig
|   /usr/lib/pkgconfig/Qt5Qwt6.pc
| Please set FILES such that these items are packaged. Alternatively if they are unneeded, avoid installing them or delete them within do_install.

Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>

recipes-qt/qwt/qwt-qt5_6.1.3.bb

@@ -25,7 +25,11 @@ EXTRA_QMAKEVARS_PRE += " \
 "
 
 do_configure_prepend() {
-    sed -i 's:/usr/local/qwt-$$QWT_VERSION:${prefix}:' ${S}/*.pri
+    sed -i \
+        -e 's:/usr/local/qwt-$$QWT_VERSION:${prefix}:' \
+        -e 's:^QWT_INSTALL_LIBS.*:QWT_INSTALL_LIBS = ${libdir}:' \
+        ${S}/*.pri
+    export QWT_INSTALL_LIBS=${libdir}
 }
 
 do_install_append() {