aarch64 libunwind compatibility fix

Grid/GridStd.h

@@ -42,6 +42,7 @@ void GridAbort(void);
 #define ASSLOG(A) ::write(STDERR_FILENO,A,::strlen(A));
 #ifdef HAVE_EXECINFO_H
 #define GRID_ASSERT(b) if(!(b)) {					\
+    fflush(stdout); \
     ASSLOG(" GRID_ASSERT failure: ");					\
     ASSLOG(__FILE__);							\
     ASSLOG(" : ");							\

Grid/util/Init.cc

@@ -755,7 +755,7 @@ void Grid_generic_handler(int sig,siginfo_t *si,void * ptr)
   sig_print_uint(si->si_code);
   SIGLOG("\n");
 
-  ucontext_t *uc= (ucontext_t *)ptr;
+  unw_context_t *uc= (unw_context_t *)ptr;
   
   SIGLOG("Backtrace:\n");
 #ifdef HAVE_UNWIND

configure.ac

@@ -409,10 +409,16 @@ AC_SEARCH_LIBS([unw_backtrace], [unwind],
                [have_unwind=true],
 	             [AC_MSG_WARN(libunwind library was not found in your system.)])
 
-AC_SEARCH_LIBS([_Ux86_64_step], [unwind-x86_64],
-               [AC_DEFINE([HAVE_UNWIND_X86_64], [1], [Define to 1 if you have the `libunwind-x86_64' library])]
-               [have_unwind_x86_64=true],
-	             [AC_MSG_WARN(libunwind library was not found in your system.)])
+AS_CASE([$host_cpu], [x86_64],
+  [AC_SEARCH_LIBS([_Ux86_64_step], [unwind-x86_64],
+                [AC_DEFINE([HAVE_UNWIND_X86_64], [1], [Define to 1 if you have the `libunwind-x86_64' library])]
+                [have_unwind_x86_64=true],
+                [AC_MSG_WARN(libunwind library was not found in your system.)])],
+  [aarch64],
+  [AC_SEARCH_LIBS([_Uaarch64_step], [unwind-aarch64],
+                [AC_DEFINE([HAVE_UNWIND_AARCH64], [1], [Define to 1 if you have the `libunwind-aarch64' library])]
+                [have_unwind_aarch64=true],
+                [AC_MSG_WARN(libunwind library was not found in your system.)])])
 
 AC_SEARCH_LIBS([SHA256_Init], [crypto],
                [AC_DEFINE([HAVE_CRYPTO], [1], [Define to 1 if you have the `OpenSSL' library])]