Switch from Travis CI to GitHub Actions

GitHub Actions should be significantly faster than Travis CI.

Author: Calinou

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/ci.yml

@@ -0,0 +1,126 @@
+name: Continuous integration
+on: [push, pull_request]
+
+jobs:
+  linux:
+    name: Build (Linux, GCC)
+    runs-on: ubuntu-16.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.4
+        with:
+          submodules: recursive
+
+      - name: Set up Python (for SCons)
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.9.1'
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -qqq build-essential pkg-config
+          python -m pip install scons
+
+      - name: Build godot-cpp
+        run: |
+          scons target=release generate_bindings=yes -j $(nproc)
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2.2.1
+        with:
+          name: godot-cpp-linux-glibc2.23-x86_64-release
+          path: bin/libgodot-cpp.linux.release.64.a
+          if-no-files-found: error
+
+  windows-msvc:
+    name: Build (Windows, MSVC)
+    runs-on: windows-2019
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.4
+        with:
+          submodules: recursive
+
+      - name: Set up Python (for SCons)
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.9.1'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install scons
+
+      - name: Build godot-cpp
+        run: |
+          scons target=release generate_bindings=yes -j $env:NUMBER_OF_PROCESSORS
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2.2.1
+        with:
+          name: godot-cpp-windows-msvc2019-x86_64-release
+          path: bin/libgodot-cpp.windows.release.64.lib
+          if-no-files-found: error
+
+  windows-mingw:
+    name: Build (Windows, MinGW)
+    runs-on: windows-2019
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.4
+        with:
+          submodules: recursive
+
+      - name: Set up Python (for SCons)
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.9.1'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install scons
+
+      - name: Build godot-cpp
+        # Install GCC from Scoop as the default supplied GCC doesn't work ("Error 1").
+        run: |
+          Invoke-Expression (New-Object System.Net.WebClient).DownloadString('https://get.scoop.sh')
+          scoop install gcc
+          g++ --version
+          gcc --version
+          scons target=release generate_bindings=yes use_mingw=yes -j $env:NUMBER_OF_PROCESSORS
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2.2.1
+        with:
+          name: godot-cpp-linux-mingw-x86_64-release
+          path: bin/libgodot-cpp.windows.release.64.a
+          if-no-files-found: error
+
+  macos:
+    name: Build (macOS, Clang)
+    runs-on: macos-11.0
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.4
+        with:
+          submodules: recursive
+
+      - name: Set up Python (for SCons)
+        uses: actions/setup-python@v2
+        with:
+          python-version: '3.9.1'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install scons
+
+      - name: Build godot-cpp
+        run: |
+          scons target=release generate_bindings=yes -j $(sysctl -n hw.logicalcpu)
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2.2.1
+        with:
+          name: godot-cpp-macos-x86_64-release
+          path: bin/libgodot-cpp.osx.release.64.a
+          if-no-files-found: error