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 "${ANSWER}" in
-    "x86_64") ;;
-    "arm64") ;;
-    "powerpc64") ;;
-    "mips64") ;;
-    "")
-      export "ANSWER=${ARCH}"
-      ;;
-    *)
-      log_error "Invalid execution architecture \"${ANSWER,,}\", please retry."
-      arch_executors
-      return
-      ;;
-  esac
-  ### MISIMPLEMENTED
+  if [ "${ANSWER}" == "" ]; then
+    echo "ARCH_EXECUTORS=${ARCH}" >> "${TMPDIR}/androot.env"
+    return
+  fi
+  for ARCHITECTURE in ${ANSWER}; do
+    case "${ARCHITECTURE}" in
+      "x86_64") ;;
+      "arm64") ;;
+      "powerpc64") ;;
+      "mips64") ;;
+      *)
+        log_error "Invalid execution architecture \"${ARCHITECTURE}\", please retry."
+        arch_executors
+        return
+        ;;
+    esac
+  done
   echo "ARCH_EXECUTORS=${ANSWER}" >> "${TMPDIR}/androot.env"
 }