Add a clang preset and use it in CI alongside gcc

Do a separate build with this preset in the CI job so that we make sure
the project is always buildable with clang as well.

While the clang build passes the test suite just fine, keep using only
the gcc build for that, to save resources and time.

Disable WERROR and sanitizers for now, as they cause configuration and
runtime errors, respectively, which is tracked via 4105 and 4112. We can
reenable these options (drop them from cacheVariables) once those
tickets are resolved.

Fixes: 4104

Author: dmnks

.github/workflows/linux.yml

@@ -18,14 +18,22 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+
+      - name: Build the Fedora testing environment (clang)
+        run: ./mktree.oci build --preset dev-clang
+        working-directory: ./tests
+
       - name: Build the Fedora testing environment (gcc)
+        # This replaces the previous clang based image
         run: ./mktree.oci build --preset dev-gcc
         working-directory: ./tests
+
       - name: Fix kernel mmap rnd bits
         # High entropy setting in GH runner images >= 20240310.1.0
         # causes ASAN blowing up here and there:
         # https://github.com/actions/runner-images/issues/9491
         run: sudo sysctl vm.mmap_rnd_bits=28
+
       - name: Run the test suite
         run: ./mktree.oci check --interactive=false -j$(nproc)
         working-directory: ./tests

CMakePresets.json

@@ -27,6 +27,18 @@
                 "CMAKE_C_COMPILER": "gcc",
                 "CMAKE_CXX_COMPILER": "g++"
             }
+        },
+        {
+            "name": "dev-clang",
+            "inherits": "dev",
+            "displayName": "Clang based development",
+            "cacheVariables": {
+                "CMAKE_C_COMPILER": "clang",
+                "CMAKE_CXX_COMPILER": "clang++",
+                "ENABLE_WERROR": "OFF",
+                "ENABLE_ASAN": "OFF",
+                "ENABLE_UBSAN": "OFF"
+            }
         }
     ]
 }

tests/Dockerfile.fedora

@@ -58,7 +58,10 @@ RUN dnf -y install \
   sequoia-sq \
   libasan \
   libubsan \
-  nss-altfiles
+  nss-altfiles \
+  clang \
+  compiler-rt \
+  libomp-devel
 # If updates to specific packages are needed, do it here
 # RUN dnf -y --enablerepo=updates install ...