GHA CI: don't override cmake default CXXFLAGS

.github/workflows/ci_windows.yaml

@@ -77,11 +77,12 @@ jobs:
             --recurse-submodules `
             https://github.com/arvidn/libtorrent.git
           cd libtorrent
+          $env:CXXFLAGS+=" /guard:cf"
+          $env:LDFLAGS+=" /guard:cf"
           cmake `
             -B build `
             -G "Ninja" `
             -DCMAKE_BUILD_TYPE=RelWithDebInfo `
-            -DCMAKE_CXX_FLAGS=/guard:cf `
             -DCMAKE_EXPORT_COMPILE_COMMANDS=ON `
             -DCMAKE_INSTALL_PREFIX="${{ env.libtorrent_path }}" `
             -DCMAKE_TOOLCHAIN_FILE="${{ env.RUNVCPKG_VCPKG_ROOT }}/scripts/buildsystems/vcpkg.cmake" `
@@ -95,11 +96,11 @@ jobs:
 
       - name: Build qBittorrent
         run: |
+          $env:CXXFLAGS+=" /WX"
           cmake `
             -B build `
             -G "Ninja" `
             -DCMAKE_BUILD_TYPE=RelWithDebInfo `
-            -DCMAKE_CXX_FLAGS="/WX" `
             -DCMAKE_EXPORT_COMPILE_COMMANDS=ON `
             -DCMAKE_TOOLCHAIN_FILE="${{ env.RUNVCPKG_VCPKG_ROOT }}/scripts/buildsystems/vcpkg.cmake" `
             -DBOOST_ROOT="${{ env.boost_path }}" `