Fix misimplemented arch_executors function

prepare.sh

@@ -37,22 +37,23 @@ function arch_executors() {
   log_info "      can be specified, if you want."
   log_info "Available execution architectures: x86_64, arm64, powerpc64, mips64"
   log_ask "Execution architecture(s): "
-  ### MISIMPLEMENTED
-  case "${ANSWER}" in
+  if [ "${ANSWER}" == "" ]; then
+    echo "ARCH_EXECUTORS=${ARCH}" >> "${TMPDIR}/androot.env"
+    return
+  fi
+  for ARCHITECTURE in ${ANSWER}; do
+    case "${ARCHITECTURE}" in
       "x86_64") ;;
       "arm64") ;;
       "powerpc64") ;;
       "mips64") ;;
-    "")
-      export "ANSWER=${ARCH}"
-      ;;
       *)
-      log_error "Invalid execution architecture \"${ANSWER,,}\", please retry."
+        log_error "Invalid execution architecture \"${ARCHITECTURE}\", please retry."
         arch_executors
         return
         ;;
     esac
-  ### MISIMPLEMENTED
+  done
   echo "ARCH_EXECUTORS=${ANSWER}" >> "${TMPDIR}/androot.env"
 }