[Ada] Implement stack unwinding for Linux on AArch64

2018-05-25  Doug Rupp  <rupp@adacore.com>

gcc/ada/

	* tracebak.c (aarch64-linux): Implement.

From-SVN: r260730

gcc/ada/ChangeLog

+2018-05-25  Doug Rupp  <rupp@adacore.com>
+
+	* tracebak.c (aarch64-linux): Implement.
+
 2018-05-25  Justin Squirek  <squirek@adacore.com>
 
 	* sem_ch8.adb: Minor reformatting.

gcc/ada/tracebak.c

@@ -516,6 +516,13 @@ struct layout
 #error Unhandled QNX architecture.
 #endif
 
+/*------------------- aarch64-linux ----------------------------------*/
+
+#elif (defined (__aarch64__) && defined (__linux__))
+
+#define USE_GCC_UNWINDER
+#define PC_ADJUST -4
+
 /*----------------------------- ia64 ---------------------------------*/
 
 #elif defined (__ia64__) && (defined (__linux__) || defined (__hpux__))