configure.ac: Use uname instead of arch.

arch is deprecated in linux-utils and coreutils does not install it by default.

https://git.kernel.org/cgit/utils/util-linux/util-linux.git/commit/?id=27abd8094845b4b2002a8ed5c3dd212999902c8f
http://www.gnu.org/software/coreutils/manual/html_node/arch-invocation.html#arch-invocation

Use uname -m, because uname -p returns unknown on alpine.

Signed-off-by: John Coyle <dx9err@gmail.com>

configure.ac

@@ -244,14 +244,7 @@ AC_CHECK_PROG(YASM_CHECK, yasm, yes)
 if test x"$YASM_CHECK" = x"yes"; then
   if yasm -f elf64 src/common/crc32c_intel_fast_asm.S -o /dev/null; then
      echo 'we have a modern and working yasm'
-     # FreeBSD has uname -p not arch(1), so do not exec arch
-     arch_x86_64=0
-     if test x`uname -p`x = x"amd64"x ; then
-	arch_x86_64=1
-     elif which arch 2>&1 > /dev/null; then 
-	test x`arch`x = x"x86_64"x  && arch_x86_64=1
-     fi
-     if test $arch_x86_64 -eq 1 ; then
+     if test x`uname -m`x = x"x86_64"x || test x`uname -m`x = x"amd64"x; then
         echo 'we are x86_64'
         arch_x32=0
         AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [[