[gcc r12-5669] [Ada] RTEMS: add traceback support for AArch64

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:621cccba3f8b0cd2757feda171e66e3820b55c2c

commit r12-5669-g621cccba3f8b0cd2757feda171e66e3820b55c2c
Author: Patrick Bernardi <bernardi@adacore.com>
Date:   Fri Nov 12 20:01:20 2021 -0500

    [Ada] RTEMS: add traceback support for AArch64
    
    gcc/ada/
    
            * tracebak.c: Add AArch64 RTEMS support.

Diff:
---
 gcc/ada/tracebak.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/ada/tracebak.c b/gcc/ada/tracebak.c
index 4f1699ffc0d..8fa5608441b 100644
--- a/gcc/ada/tracebak.c
+++ b/gcc/ada/tracebak.c
@@ -551,6 +551,18 @@ is_return_from(void *symbol_addr, void *ret_addr)
 #error Unhandled QNX architecture.
 #endif
 
+/*---------------------------- RTEMS ---------------------------------*/
+
+#elif defined (__rtems__)
+
+#define USE_GCC_UNWINDER
+
+#if defined (__aarch64__)
+#define PC_ADJUST -4
+#else
+#error Unhandled RTEMS architecture.
+#endif
+
 /*------------------- aarch64-linux ----------------------------------*/
 
 #elif (defined (__aarch64__) && defined (__linux__))