[COMMITTED 09/45] ada: Fix fallout of recent change related to task activation

[Marc Poulhiès]

From: Eric Botcazou <ebotca...@adacore.com>

The Move_Activation_Chain routine is not available in all runtime libraries.

gcc/ada/ChangeLog:

        * exp_ch6.adb (Expand_N_Extended_Return_Statement): Do not call
        Move_Activation_Chain if it is not available in the runtime library.

Tested on x86_64-pc-linux-gnu (before the recent bootstrap breakage), committed 
on master.

---
 gcc/ada/exp_ch6.adb | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gcc/ada/exp_ch6.adb b/gcc/ada/exp_ch6.adb
index 48627649a30..981cb2c8684 100644
--- a/gcc/ada/exp_ch6.adb
+++ b/gcc/ada/exp_ch6.adb
@@ -5920,6 +5920,12 @@ package body Exp_Ch6 is
 
       function Move_Activation_Chain (Func_Id : Entity_Id) return Node_Id is
       begin
+         --  Move_Activation_Chain is not universally available
+
+         if not RTE_Available (RE_Move_Activation_Chain) then
+            return Make_Null_Statement (Loc);
+         end if;
+
          return
            Make_Procedure_Call_Statement (Loc,
              Name                   =>
-- 
2.51.0