Add a clang preset and use it in CI alongside gcc

This preset configures the project for building with clang. Use it in
the GH workflow to do a test build, to make sure we can also build with
clang successfully.

Keep using the gcc based image for testing, though, as that's the more
common setup in rpm based distros, and running the test-suite twice
would be wasteful. That said, the test-suite does indeed pass with this
preset.

Disable WERROR and ASAN/UBSAN for now, though, as those currently cause
configuration and runtime errors, respectively, which is tracked via the
tickets rpm-software-management#4105 and rpm-software-management#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 ...