title: telegram not compile with ndk 18
body: <p>When i try compile telegram with android studio 3.2, i get an error:
      Android NDK: Invalid NDK_TOOLCHAIN_VERSION value: 4.9. GCC is no longer supported.
  I know, what from version of android ndk 18 and more gcc is no longer supported, but how i can fix this error in telegram, or it's better wait new version of telegram on github? When i tryed delete string in application.nk file,connected with version of toolch, i got another errors, connected with cpp files. Help me please compile telegram,without downgrading ndk. Thanks everybody for the help.</p>