nixpkgs/pkgs/development/libraries/qt-5/5.8/qtbase/nix-profiles-library-paths.patch

Index: qtbase-opensource-src-5.8.0/src/corelib/kernel/qcoreapplication.cpp
===================================================================
--- qtbase-opensource-src-5.8.0.orig/src/corelib/kernel/qcoreapplication.cpp
+++ qtbase-opensource-src-5.8.0/src/corelib/kernel/qcoreapplication.cpp
@@ -2476,6 +2476,15 @@ QStringList QCoreApplication::libraryPat
         QStringList *app_libpaths = new QStringList;
         coreappdata()->app_libpaths.reset(app_libpaths);
 
+        // Add library paths derived from NIX_PROFILES.
+        const QByteArrayList profiles = qgetenv("NIX_PROFILES").split(' ');
+        const QString plugindir = QString::fromLatin1("/lib/qt5/plugins");
+        for (const QByteArray &profile: profiles) {
+            if (!profile.isEmpty()) {
+                app_libpaths->append(QFile::decodeName(profile) + plugindir);
+            }
+        }
+
         const QByteArray libPathEnv = qgetenv("QT_PLUGIN_PATH");
         if (!libPathEnv.isEmpty()) {
             QStringList paths = QFile::decodeName(libPathEnv).split(QDir::listSeparator(), QString::SkipEmptyParts);