Respect TDESKTOP_DISABLE_GTK_INTEGRATION.

Telegram/CMakeLists.txt

@@ -1009,6 +1009,7 @@ elseif (APPLE)
         endif()
     endif()
 elseif (LINUX)
+    if (NOT TDESKTOP_DISABLE_GTK_INTEGRATION)
         find_package(PkgConfig REQUIRED)
 
         pkg_check_modules(GTK2 REQUIRED gtk+-2.0)
@@ -1037,6 +1038,7 @@ elseif (LINUX)
             message(FATAL_ERROR "No libappindicator found by pkg-config.")
         endif()
     endif()
+endif()
 
 if (build_macstore)
     set(bundle_identifier "org.telegram.desktop")