Disable Spawn on both Linux and Windows

Too many issues have been detected when using Spawn
as the default API to laucnh external processes, so
revert back to the old GPS.Kernel.Timeout API until
we solve the identified issues.

For eng/ide/eng/ide/gnatstudio#538

Author: AnthonyLeonardoGracio

kernel/src/gps-kernel-spawns.adb

@@ -36,7 +36,10 @@ with Commands;
 
 package body GPS.Kernel.Spawns is
 
-   Me : constant Trace_Handle := Create ("GPS.KERNEL.SPAWN");
+   Me : constant Trace_Handle := Create ("GPS.KERNEL.SPAWN", Off);
+   --  Disable Spawn as the default API to launch external processes
+   --  until we solve the remaining issues (#538 and #495).
+
    Me_IO : constant Trace_Handle := Create
      ("GPS.KERNEL.SPAWN_IO", Off);
 
@@ -424,7 +427,7 @@ package body GPS.Kernel.Spawns is
       end if;
 
       if Console /= null then
-         Trace (Me, "Connect the command_handler to the console");
+         Trace (Me_IO, "Connect the command_handler to the console");
          Console.Set_Command_Handler (Input_Handler'Access, Obj.all'Address);
 
          Obj.Console := Console;
@@ -447,7 +450,7 @@ package body GPS.Kernel.Spawns is
         (Spawn.Process_Listeners.Process_Listener_Access (Obj));
 
       Trace
-        (Me, "Spawning " & GNATCOLL.Arg_Lists.To_Display_String (Arg_List));
+        (Me_IO, "Spawning " & GNATCOLL.Arg_Lists.To_Display_String (Arg_List));
 
       Obj.Ref;  --  Keep command alive until process finishes
       Obj.Process.Start;

testsuite/tests/gs.507.no_silent_exit/test.py

@@ -13,7 +13,8 @@ def run_test():
     yield wait_tasks()
 
     gps_assert(
-        "process exited with status" in GPS.Console("Run: foo" + dot_exe).get_text(),
+        "Could not locate executable" in GPS.Console().get_text(),
         True,
-        "Missing message in the Messages view",
-    )
+        "We should have a message warning that the executable could "
+        + "not be found in the Messages view",
+    )