small fix #160

	name: Compile Library

	on:
	push:
	paths-ignore:
	- '.github/workflows/cpp_lint.yml'
	- '.github/workflows/compile_examples.yml'
	- 'examples/**'
	pull_request:
	paths-ignore:
	- '.github/workflows/cpp_lint.yml'
	- '.github/workflows/compile_examples.yml'
	- 'examples/**'

	jobs:
	build:

	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	board:
	- "nodemcuv2"
	- "lolin32"
	- "nucleo_l152re"

	steps:
	- uses: actions/checkout@v2
	- name: Cache pip
	uses: actions/cache@v2
	with:
	path: ~/.cache/pip
	key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
	restore-keys: ${{ runner.os }}-pip-
	- name: Cache PlatformIO
	uses: actions/cache@v2
	with:
	path: ~/.platformio
	key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}
	- name: Set up Python
	uses: actions/setup-python@v2
	- name: Install PlatformIO
	run: \|
	python -m pip install --upgrade pip
	pip install --upgrade platformio

	- name: Create main file
	run: \|
	echo "#include <Arduino.h>" >> src/main.ino
	echo "void setup() {}" >> src/main.ino
	echo "void loop() {}" >> src/main.ino

	- name: Run PlatformIO
	run: pio ci --board=${{ matrix.board }} src

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