Try using -Wsuggest-override in the CI builds

This is a useful warning and we want to ensure that wx compiles cleanly
with it.

Note that it can't be used for gcc < 11 (it is supported by it since 5.1
but there are tons of false positives for the macros from wx/rtti.h with
the older versions) and only relatively recent clang supports this
gcc-compatible option.

.github/workflows/ci.yml

@@ -105,21 +105,25 @@ jobs:
             container: ubuntu:20.04
             compiler: clang++-10
             configure_flags: --disable-sys-libs
+            extra_warnings: -Winconsistent-missing-override
             use_xvfb: true
           - name: Ubuntu 22.04 wxGTK with wx containers
             runner: ubuntu-22.04
             configure_flags: --enable-compat30 --disable-std_containers
+            extra_warnings: -Wsuggest-override
             use_xvfb: true
             check_headers: true
           - name: Ubuntu 24.04 wxGTK with ASAN
             runner: ubuntu-24.04
             configure_flags: --disable-compat32 --disable-sys-libs
+            extra_warnings: -Wsuggest-override
             skip_samples: true
             use_asan: true
             use_xvfb: true
           - name: Ubuntu 24.04 wxGTK with UBSAN
             runner: ubuntu-24.04
             configure_flags: --with-cxx=20
+            extra_warnings: -Wsuggest-override
             use_ubsan: true
             use_xvfb: true
             build_out_of_tree_samples: true
@@ -270,7 +274,7 @@ jobs:
 
           if [ -z ${{ matrix.allow_warnings }} ]; then
             if [ -z ${{ matrix.allow_extra_warnings }} ]; then
-              error_opts="-Wextra"
+              error_opts="-Wextra ${{ matrix.extra_warnings }}"
             fi
             error_opts="$error_opts -Werror $allow_warn_opt"
             echo "wxMAKEFILE_ERROR_CXXFLAGS=$error_opts" >> $GITHUB_ENV

.github/workflows/ci_mac.yml

@@ -141,7 +141,7 @@ jobs:
             ;;
         esac
         if [ -z ${{ matrix.allow_warnings }} ]; then
-          error_opts="-Werror $allow_warn_opt"
+          error_opts="-Werror -Wsuggest-override $allow_warn_opt"
           echo "wxMAKEFILE_ERROR_CXXFLAGS=$error_opts" >> $GITHUB_ENV
           echo "wxMAKEFILE_CXXFLAGS=$wxMAKEFILE_CXXFLAGS $error_opts" >> $GITHUB_ENV
         fi

.github/workflows/ci_msw.yml

@@ -176,7 +176,7 @@ jobs:
           cmake -G "MinGW Makefiles" \
                 -DCMAKE_C_COMPILER=clang.exe \
                 -DCMAKE_CXX_COMPILER=clang++.exe \
-                -DCMAKE_CXX_FLAGS=-Werror \
+                -DCMAKE_CXX_FLAGS="-Werror -Wsuggest-override" \
                 -DCMAKE_BUILD_TYPE=Release \
                 -DwxBUILD_SAMPLES=ALL \
                 -DwxBUILD_TESTS=ALL \