Forbid '--target' and '--RTS' in GNATcheck switches

Do this because similar GPR attributes already exist.

Author: HugoGGuerrier

lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst

@@ -380,6 +380,8 @@ GNATcheck:
     * ``-eL``
     * ``-r, --rule [rule_name]`` (use ``Rules`` attribute instead)
     * ``--rule-file=filename`` (use ``Rule_File`` attribute instead)
+    * ``--target`` (use the ``Target`` GPR attribute instead)
+    * ``--RTS`` (use the ``Runtime`` GPR attribute instead)
 
     If you're providing one of those switches through the ``Switches`` or the
     ``Default_Switches`` attribute, GNATcheck will emit an error message and

lkql_checker/src/gnatcheck-projects.adb

@@ -1268,6 +1268,8 @@ package body Gnatcheck.Projects is
             Disallow (Arg.Follow_Symbolic_Links.This, "-eL" & In_Project_Msg);
             Disallow (Arg.Rules.This, "-r" & In_Project_Msg);
             Disallow (Arg.Rule_File.This, "--rule-file" & In_Project_Msg);
+            Disallow (Arg.Target.This, "--target" & In_Project_Msg);
+            Disallow (Arg.RTS.This, "--RTS" & In_Project_Msg);
          end;
       end if;
 
@@ -1291,6 +1293,8 @@ package body Gnatcheck.Projects is
          Allow (Arg.Follow_Symbolic_Links.This);
          Allow (Arg.Rules.This);
          Allow (Arg.Rule_File.This);
+         Allow (Arg.Target.This);
+         Allow (Arg.RTS.This);
       end if;
 
       loop