configure: Fix type of argument to backtrace_symbols

The backtrace_symbols function expects a pointer to an array of
void * values, not a pointer to an array of a single element.
Removing the address operator ensures that the right type is used.

This avoids an unconditional failure of this probe with compilers
that treat incompatible pointer types as a compilation error.

configure

@@ -14418,7 +14418,7 @@ main (void)
 {
 
       void *sym[1];
-      backtrace_symbols(&sym, sizeof(sym))
+      backtrace_symbols(sym, sizeof(sym))
   ;
   return 0;
 }

configure.ac

@@ -2163,7 +2163,7 @@ if test "x$ac_cv_header_execinfo_h" = "xyes"; then
       #include <execinfo.h>
     ]], [[
       void *sym[1];
-      backtrace_symbols(&sym, sizeof(sym)) ]])],[
+      backtrace_symbols(sym, sizeof(sym)) ]])],[
       AC_MSG_RESULT(yes)
       ac_cv_lib_execinfo_backtrace_symbols="yes"
     ],[