Restrict gnat.dg/system_info1.adb to Linux and Windows hosts

Where it is know to work, still covering the original test intent.

From-SVN: r275999

gcc/testsuite/ChangeLog

+2019-09-20  Olivier Hainque  <hainque@adacore.com>
+
+	* gnat.dg/system_info1.adb: Restrict to *-*-linux* and *-*-mingw*.
+
 2019-09-20  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* gcc.dg/pr91269.c: New test.

gcc/testsuite/gnat.dg/system_info1.adb

---  { dg-do run }
+--  A basic test initially intended to check that
+--  System.Task_Info.Number_Of_Processors yields sensible results on
+--  both 32bit and 64bit Windows. Additional configurations where the
+--  feature was verified to work can opt-in.
+
+--  { dg-do run { target *-*-mingw* *-*-linux* } }
 
 with System.Multiprocessors;
 with System.Task_Info;
@@ -20,4 +25,4 @@ begin
    if Nprocs /= Integer (Ncpus) then
       raise Program_Error;
    end if;
-end;
+end;
\ No newline at end of file