Autotools CI for Github actions

.github/workflows/autotools.yml

+name: Autotools
+
+on: [push, pull_request]
+
+jobs:
+
+ AutoMakeBuild:
+    name: AutoMake/${{ matrix.config.name }}
+    runs-on: ${{ matrix.config.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+        - {
+            name: "Linux/GCC",
+            os: ubuntu-latest,
+            compiler: gcc,
+            automakeconfig:
+          }
+        - {
+            name: "Linux/GCC/EnableAssertions",
+            os: ubuntu-latest,
+            compiler: gcc,
+            buildconfig: --enable-assertions
+          }
+        - {
+            name: "Linux/GCC/EnableCustomModes",
+            os: ubuntu-latest,
+            compiler: gcc,
+            buildconfig: --enable-assertions --enable-custom-modes
+          }
+    steps:
+      - uses: actions/checkout@v3
+      - name: Pull git submodules
+        run: git submodule update --init --recursive
+        # No AutoMake on Mac so let's install it
+      - name: Install AutoConf, AutoMake and LibTool on MacOSX
+        if: matrix.config.os == 'macos-latest'
+        run: brew install autoconf automake libtool
+      - name: Autogen
+        run: CC=${{ matrix.config.compiler }} ./autogen.sh
+      - name: Configure
+        run: CFLAGS="-mavx -mfma -mavx2 -O2 -ffast-math" ./configure --enable-float-approx ${{ matrix.config.buildconfig }}
+      - name: Build
+        run: make -j 2
+      - name: Test
+        run: make check -j 2
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