Replace gfortran in CI with flang-new

.github/workflows/CI.yml

@@ -1,4 +1,4 @@
-name: CI
+name: Build with LLVM Flang
 
 on: [push, pull_request]
 
@@ -8,11 +8,12 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [macOS-12, ubuntu-24.04]
+        os: [ubuntu-24.04]
       fail-fast: true
+    container: gmao/llvm-flang:latest
     env:
-      FC: gfortran
-      GCC_V: 14
+      FC: flang-new
+      CC: clang
 
     steps:
     - name: Checkout code
@@ -22,28 +23,12 @@ jobs:
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
 
-    - name: Install Dependencies MacOS
-      if: contains(matrix.os, 'mac')
-      run: |
-        brew install gcc@${GCC_V}
-        sudo ln -s $(which gfortran-${GCC_V}) $(dirname $(which gfortran-${GCC_V}))/gfortran
-
-    - name: Install on Ubuntu
-      if: contains(matrix.os, 'ubuntu')
-      run: |
-        sudo apt update
-        sudo apt install -y build-essential gfortran-14 gcc-14 g++-14
-
-    - name: Build and Test MacOS
-      if: contains(matrix.os, 'mac')
-      run: |
-        export PATH="${HOME}/.local/bin:$PATH"
-        ./setup.sh
-
-    - name: Build and Test Ubuntu
+    - name: Build and Test with LLVM Flang
       if: contains(matrix.os, 'ubuntu')
       run: |
         fpm --version
-        export FPM_FC=gfortran-14
-        export FPM_CC=gcc-14
-        fpm test
+        $FC --version
+        $CC --version
+        export FPM_FC=$FC
+        export FPM_CC=$CC
+        fpm test --flag "-mmlir -allow-assumed-rank -O3"