[COMMITTED] ada: Fix error and crash on imported function with precondition and 'Base

["Marc Poulhiès" <poulhies@adacore.com>]

From: Eric Botcazou <ebotcazou@adacore.com>

This fixes a spurious error on an imported function with a precondition
and a parameter declared with a 'Base formal type, and even a crash in
the case where this function is declared in a generic package.

gcc/ada/

	* freeze.adb (Wrap_Imported_Subprogram): Use Copy_Subprogram_Spec
	to copy the spec from the subprogram to the generated subprogram
	body.
	(Freeze_Entity): Do not wrap imported subprograms inside generics.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/freeze.adb | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb
index f54ae0503a1..df3b5ec944e 100644
--- a/gcc/ada/freeze.adb
+++ b/gcc/ada/freeze.adb
@@ -6127,8 +6127,7 @@ package body Freeze is
 
             Bod :=
               Make_Subprogram_Body (Loc,
-                Specification              =>
-                  Copy_Separate_Tree (Spec),
+                Specification              => Copy_Subprogram_Spec (Spec),
                 Declarations               => New_List (
                   Make_Subprogram_Declaration (Loc,
                     Specification => Copy_Separate_Tree (Spec)),
@@ -6438,7 +6437,9 @@ package body Freeze is
 
             --  Check for needing to wrap imported subprogram
 
-            Wrap_Imported_Subprogram (E);
+            if not Inside_A_Generic then
+               Wrap_Imported_Subprogram (E);
+            end if;
 
             --  Freeze all parameter types and the return type (RM 13.14(14)).
             --  However skip this for internal subprograms. This is also where
-- 
2.40.0