tests/tcg: Use $cpu in configure.sh

Use $cpu instead of $ARCH, which has been removed from
the top-level configure.

Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Fixes: 823eb01345 ("configure, meson: move ARCH to meson.build")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

configure

@@ -3821,7 +3821,7 @@ done
 (for i in $cross_cc_vars; do
   export $i
 done
-export target_list source_path use_containers ARCH
+export target_list source_path use_containers cpu
 $source_path/tests/tcg/configure.sh)
 
 # temporary config to build submodules

tests/tcg/configure.sh

@@ -326,7 +326,7 @@ for target in $target_list; do
   elif test $got_cross_cc = no && test "$container" != no && \
           test -n "$container_image"; then
       for host in $container_hosts; do
-          if test "$host" = "$ARCH"; then
+          if test "$host" = "$cpu"; then
               echo "DOCKER_IMAGE=$container_image" >> $config_target_mak
               echo "DOCKER_CROSS_CC_GUEST=$container_cross_cc" >> \
                    $config_target_mak