Do not build unicode_to_keysym.cc when use_x11 == 0

remoting/host/BUILD.gn

Index: remoting/host/BUILD.gn
diff --git a/remoting/host/BUILD.gn b/remoting/host/BUILD.gn
index 8a918fa432492d302b1f47a308a3be190b3bbfb5..5f8b41e1a2bd710e19dc6c38cc552f6b3c5b9497 100644
--- a/remoting/host/BUILD.gn
+++ b/remoting/host/BUILD.gn
@@ -109,6 +109,7 @@ if (is_mac) {  # TODO(GYP) Mac build of remoting host.
       if (is_linux) {
         # These will already be filtered out on non-Linux.
         sources -= [
+          "linux/unicode_to_keysym.cc",
           "linux/x11_util.cc",
           "linux/x_server_clipboard.cc",
           "linux/x_server_clipboard.h",
@@ -298,6 +299,9 @@ if (is_mac) {  # TODO(GYP) Mac build of remoting host.
       "win/worker_process_launcher_unittest.cc",
     ]
 
+    if (!use_x11 && is_linux) {
+      sources -= [ "linux/unicode_to_keysym_unittest.cc" ]
+    }
     if (use_ozone || is_chromeos) {
       sources -= [ "local_input_monitor_unittest.cc" ]
     }