perf env: Adopt perf_env__arch() from the annotate code

And use it in the libunwind case, with both passing a valid perf_env to
extract the arch to be normalized from and passing NULL with the same
semantic as in the annotate code: to get it from uname() uts.machine.

Now the code to generate per arch errno translation tables (int/string)
can use it to decode perf.data files recorded in a different arch than
that where 'perf trace' (or any other analysis tool) runs.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-p2epffgash69w38kvj3ntpc9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate.c

@@ -26,7 +26,6 @@
 #include <pthread.h>
 #include <linux/bitops.h>
 #include <linux/kernel.h>
-#include <sys/utsname.h>
 
 #include "sane_ctype.h"
 
@@ -1420,21 +1419,6 @@ fallback:
 	return 0;
 }
 
-static const char *perf_env__arch(struct perf_env *env)
-{
-	struct utsname uts;
-	char *arch_name;
-
-	if (!env) { /* Assume local operation */
-		if (uname(&uts) < 0)
-			return NULL;
-		arch_name = uts.machine;
-	} else
-		arch_name = env->arch;
-
-	return normalize_arch(arch_name);
-}
-
 static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
 {
 	struct map *map = args->map;