update to latest j2cl and gwt and migrate to javs 11 #49

	#
	# Copyright © 2018 The GWT Project Authors
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.
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	name: CI

	on: [push, pull_request]

	jobs:
	build:
	runs-on: ubuntu-latest

	steps:
	- name: Check out Git repository
	uses: actions/checkout@v3

	- name: Install Java and Maven
	uses: actions/setup-java@v3
	with:
	java-version: 11
	distribution: 'temurin'

	# TODO: cache dependencies (taking into accounts: Maven plugins, snapshots, etc.)

	- name: Build with Maven
	run: JAVA_HOME=$JAVA_HOME_8_X64 mvn -V -B -ntp -U -e verify

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