ci/msys2: add build with -ftrivial-auto-var-init

Just to catch uninitialized variables early. Build all three                                                                                          unint/zero/pattern to compare the results between them and we don't                                                                                   accidentally depend on implicit initialization in tests.

.github/workflows/build.yml

@@ -572,9 +572,16 @@ jobs:
         include:
           - sys: "clang64"
             os: "windows-latest"
+            auto-var-init: "uninitialized"
           - sys: "clang64"
             os: "windows-latest"
             asan: true
+          - sys: "clang64"
+            os: "windows-latest"
+            auto-var-init: "zero"
+          - sys: "clang64"
+            os: "windows-latest"
+            auto-var-init: "pattern"
           - sys: "mingw64"
             os: "windows-latest"
           - sys: "ucrt64"
@@ -631,6 +638,7 @@ jobs:
         env:
           SYS: ${{ matrix.sys }}
           ASAN: ${{ matrix.asan }}
+          AUTO_VAR_INIT: ${{ matrix.auto-var-init }}
 
       - name: Print meson log
         if: ${{ failure() && steps.build.outcome == 'failure' }}

ci/build-msys2.sh

@@ -14,6 +14,13 @@ if [[ -n "$ASAN" ]]; then
     )
 fi
 
+if [[ -n "$AUTO_VAR_INIT" ]]; then
+    args+=(
+        -Dc_args="-ftrivial-auto-var-init=$AUTO_VAR_INIT"
+        -Dcpp_args="-ftrivial-auto-var-init=$AUTO_VAR_INIT"
+    )
+fi
+
 echo "::group::Building subrandr"
 build_subrandr "/$SYS"
 echo "::endgroup::"