Fix install in kf<version>

kcm/backends/firewalld/CMakeLists.txt

@@ -18,7 +18,7 @@ set(firewalld_backend_SRCS
 kcoreaddons_add_plugin(
     firewalldbackend
     SOURCES ${firewalld_backend_SRCS}
-    INSTALL_NAMESPACE "kf5/plasma_firewall")
+    INSTALL_NAMESPACE "kf${QT_MAJOR_VERSION}/plasma_firewall")
 
 target_link_libraries(firewalldbackend
     Qt::DBus

kcm/backends/ufw/CMakeLists.txt

@@ -11,7 +11,7 @@ set(ufw_backend_SRCS
 kcoreaddons_add_plugin(
     ufwbackend
     SOURCES ${ufw_backend_SRCS}
-    INSTALL_NAMESPACE "kf5/plasma_firewall")
+    INSTALL_NAMESPACE "kf${QT_MAJOR_VERSION}/plasma_firewall")
 
 target_link_libraries(ufwbackend
     kcm_firewall_core

kcm/core/firewallclient.cpp

@@ -301,7 +301,7 @@ void FirewallClient::setBackend(const QStringList &backendList)
         m_currentBackend = nullptr;
     }
 
-    const auto plugins = KPluginMetaData::findPlugins(QStringLiteral("kf5/plasma_firewall"));
+    const auto plugins = KPluginMetaData::findPlugins(QStringLiteral("kf" QT_STRINGIFY(QT_VERSION_MAJOR) "/plasma_firewall"));
 
     QList<KPluginFactory*> factories;
     for (const KPluginMetaData &metadata : plugins) {