aarch64: Implement support for elf_aux_info(3) on FreeBSD and OpenBSD

FreeBSD 12.0+, OpenBSD -current and what will be OpenBSD 7.6 support
elf_aux_info(3).

Signed-off-by: Brad Smith <brad@comstyle.com>

configure

@@ -2367,6 +2367,7 @@ SYSTEM_FUNCS="
     clock_gettime
     closesocket
     CommandLineToArgvW
+    elf_aux_info
     fcntl
     getaddrinfo
     getauxval
@@ -6579,6 +6580,7 @@ check_func_headers mach/mach_time.h mach_absolute_time
 check_func_headers stdlib.h getenv
 check_func_headers sys/stat.h lstat
 check_func_headers sys/auxv.h getauxval
+check_func_headers sys/auxv.h elf_aux_info
 check_func_headers sys/sysctl.h sysctlbyname
 
 check_func_headers windows.h GetModuleHandle

libavutil/aarch64/cpu.c

@@ -20,7 +20,7 @@
 #include "libavutil/cpu_internal.h"
 #include "config.h"
 
-#if (defined(__linux__) || defined(__ANDROID__)) && HAVE_GETAUXVAL
+#if HAVE_GETAUXVAL || HAVE_ELF_AUX_INFO
 #include <stdint.h>
 #include <sys/auxv.h>
 

libavutil/cpu.c

@@ -49,7 +49,7 @@
 #include <unistd.h>
 #endif
 
-#if HAVE_GETAUXVAL
+#if HAVE_GETAUXVAL || HAVE_ELF_AUX_INFO
 #include <sys/auxv.h>
 #endif
 
@@ -292,6 +292,13 @@ unsigned long ff_getauxval(unsigned long type)
 {
 #if HAVE_GETAUXVAL
     return getauxval(type);
+#elif HAVE_ELF_AUX_INFO
+    unsigned long aux = 0;
+    int ret = elf_aux_info(type, &aux, sizeof(aux));
+    if (ret != 0) {
+        errno = ret;
+    }
+    return aux;
 #else
     errno = ENOSYS;
     return 0;