Add CI job to build C sources with GCC 8.5

* See #4048

Author: eregon

.github/workflows/main.yml

@@ -174,6 +174,20 @@ jobs:
       env:
         PRISM_BUILD_MINIMAL: "1"
 
+  build-with-old-gcc:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v6
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ruby
+        bundler-cache: true
+    - name: Generate templates on host
+      run: bundle exec rake templates
+    - name: Build with old GCC
+      run: docker build -f rakelib/almalinux-8.dockerfile .
+
   build-java:
     runs-on: ubuntu-latest
     env:

rakelib/almalinux-8.dockerfile

@@ -0,0 +1,5 @@
+FROM almalinux:8
+RUN dnf install -y make gcc
+ADD . /prism
+WORKDIR /prism
+RUN make