Guard dpi_aware.cpp with #ifdef OS_WIN instead of CMake exclusion

Platform guards in C++ source are self-documenting and consistent with
CEF's own approach; CMake one-off filename exceptions are fragile.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: linesight

src/client_handler/CMakeLists.txt

@@ -10,8 +10,6 @@ foreach(_f IN LISTS _all_cpp)
     set(_skip FALSE)
     if(_name MATCHES "_win\\.cpp$" AND NOT WIN32)
         set(_skip TRUE)
-    elseif(_name STREQUAL "dpi_aware.cpp" AND NOT WIN32)
-        set(_skip TRUE)
     elseif(_name MATCHES "_linux\\.cpp$" AND NOT CMAKE_SYSTEM_NAME STREQUAL "Linux")
         set(_skip TRUE)
     elseif(_name MATCHES "_mac\\.(cpp|mm)$" AND NOT APPLE)

src/client_handler/dpi_aware.cpp

@@ -4,6 +4,8 @@
 
 // Windows only
 
+#ifdef OS_WIN
+
 #pragma comment(lib, "Gdi32.lib")
 #include <math.h>
 
@@ -227,3 +229,4 @@ void SetBrowserDpiSettings(CefRefPtr<CefBrowser> cefBrowser,
     );
 }
 
+#endif  // OS_WIN