Add TravisCI support for ESP-IDF v4.1-beta1.

.travis.yml

@@ -1,33 +1,37 @@
+os: linux
 dist: bionic
 language: python
 python: "3.8"
 
-before_install:
-  # Save path to the git respository
-  - PROJECT_PATH=$(pwd)
-
+jobs:
+  include:
+    - stage:  # IDF v3.3
       install:
-  # Install ESP32 toochain following steps as desribed
+        # Install ESP32 toochain following steps as described
         # in http://esp-idf.readthedocs.io/en/latest/linux-setup.html
         #
-  # Get required packages - already done above, see addons: apt: packages:
-  # - sudo apt-get install git wget make libncurses-dev flex bison gperf python python-serial
-  # Prepare directory for the toolchain
-  - mkdir -p ~/esp
-  - cd ~/esp
         # Download binary toolchain for the ESP32
+        - pushd ~
         - wget https://dl.espressif.com/dl/xtensa-esp32-elf-linux64-1.22.0-80-g6c4433a-5.2.0.tar.gz
         - tar -xzf xtensa-esp32-elf-linux64-1.22.0-80-g6c4433a-5.2.0.tar.gz
         # Make xtensa-esp32-elf available for all terminal sessions
-  - export PATH=$PATH:$HOME/esp/xtensa-esp32-elf/bin
+        - export PATH=$PATH:$(pwd)/xtensa-esp32-elf/bin
         # Get ESP-IDF from github
-  - git clone --recursive --branch v3.3 --single-branch --shallow-submodules https://github.com/espressif/esp-idf.git
+        - git clone --recursive --branch v3.3 --single-branch --shallow-submodules https://github.com/espressif/esp-idf.git esp-idf
         # Set the path to ESP-IDF directory
-  - export IDF_PATH=~/esp/esp-idf
+        - export IDF_PATH=$(pwd)/esp-idf
         # Install python dependencies
         - pip install --requirement $IDF_PATH/requirements.txt
-
+        - popd
       script:
-  # Build project within the original repository
-  - cd $PROJECT_PATH
         - $IDF_PATH/tools/idf.py build
+
+    - stage:  # IDF v4.1-beta1
+      install:
+        - pushd ~
+        - git clone --recursive --branch v4.1-beta1 --single-branch --shallow-submodules https://github.com/espressif/esp-idf.git esp-idf
+        - esp-idf/install.sh
+        - popd
+      script:
+        - source ~/esp-idf/export.sh && idf.py build
+