Add gfortran

Author: termoshtt

.github/workflows/rust.yml

@@ -82,6 +82,10 @@ jobs:
     - uses: actions/checkout@v1
       with:
         submodules: 'recursive'
+    - name: Install gfortran by apt
+      run: |
+        apt update
+        apt install -y gfortran
     - name: Install OpenBLAS by apt
       run: |
         apt update