Use #ifdef to check for __WXMSW__ and __WXGTK__ and not #if.

Using #if doesn't work when symbols are not defined.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62729 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/graphicc.cpp

@@ -1799,10 +1799,10 @@ wxGraphicsContext * wxCairoRenderer::CreateContext( const wxPrinterDC& dc)
 
 wxGraphicsContext * wxCairoRenderer::CreateContextFromNativeContext( void * context )
 {
-#if __WXMSW__
+#ifdef __WXMSW__
     return new wxCairoContext(this,(HDC)context);
 #endif
-#if __WXGTK__
+#ifdef __WXGTK__
     return new wxCairoContext(this,(cairo_t*)context);
 #endif
 }