Fix webview msvc build

Signed-off-by: falkTX <falktx@falktx.com>

cmake/DPF-plugin.cmake

@@ -996,8 +996,13 @@ function(dpf__add_plugin_specific_ui_sources NAME USE_WEB_VIEW)
   elseif(WIN32 AND USE_WEB_VIEW)
     target_sources("${NAME}" PRIVATE
       "${DPF_ROOT_DIR}/distrho/DistrhoUI_win32.cpp")
-    set_source_files_properties("${DPF_ROOT_DIR}/distrho/DistrhoUI_win32.cpp"
-      PROPERTIES COMPILE_FLAGS -std=gnu++17)
+    if (MSVC)
+      set_source_files_properties("${DPF_ROOT_DIR}/distrho/DistrhoUI_win32.cpp"
+        PROPERTIES COMPILE_FLAGS /std:c++17)
+    else()
+      set_source_files_properties("${DPF_ROOT_DIR}/distrho/DistrhoUI_win32.cpp"
+        PROPERTIES COMPILE_FLAGS -std=gnu++17)
+    endif()
   endif()
 endfunction()
 

distrho/extra/WebViewWin32.hpp

@@ -24,7 +24,7 @@
 
 START_NAMESPACE_DISTRHO
 
-struct WebView;
+class WebView;
 
 WebView* webview_choc_create(const WebViewOptions& opts);
 void webview_choc_destroy(WebView*);

distrho/src/DistrhoUtils.cpp

@@ -19,6 +19,7 @@
 #endif
 
 #include "../extra/String.hpp"
+#include "../DistrhoPluginUtils.hpp"
 #include "../DistrhoStandaloneUtils.hpp"
 
 #ifdef DISTRHO_OS_WINDOWS