Ensure frame table is 8-aligned on ARM64 and PPC64

Fixes issue ocaml#7887.

Changes

@@ -9,6 +9,9 @@ Working version
   iOS and other Darwin targets.
   (Mark Shinwell, review by Nicolas Ojeda Bar and Xavier Leroy)
 
+- #7887: ensure frame table is 8-aligned on ARM64 and PPC64
+  (Xavier Leroy, report by Mark Hayden)
+
 - #8507: Shorten symbol names of anonymous functions in Flambda mode
   (the directory portions are now hidden)
   (Mark Shinwell, review by Nicolás Ojeda Bär)

asmcomp/arm64/emit.mlp

@@ -979,7 +979,8 @@ let end_assembly () =
   `	.quad	0\n`;  (* PR#6329 *)
   `	.globl	{emit_symbol lbl_end}\n`;
   `{emit_symbol lbl_end}:\n`;
-  `	.long	0\n`;
+  `	.quad	0\n`;
+  `	.align	3\n`;  (* #7887 *)
   let lbl = Compilenv.make_symbol (Some "frametable") in
   `	.globl	{emit_symbol lbl}\n`;
   `{emit_symbol lbl}:\n`;

asmcomp/power/emit.mlp

@@ -1177,6 +1177,7 @@ let end_assembly() =
   `	{emit_string datag}	0\n`;
   (* Emit the frame descriptors *)
   emit_string data_space;  (* not rodata_space because it contains relocations *)
+  if ppc64 then `	.align  3\n`;   (* #7887 *)
   let lbl = Compilenv.make_symbol (Some "frametable") in
   declare_global_data lbl;
   `{emit_symbol lbl}:\n`;