explicitly write an 8 bit empty string

vcl/Library_vcl.mk

@@ -53,7 +53,7 @@ $(eval $(call gb_Library_set_include,vcl,\
 ))
 
 $(eval $(call gb_Library_add_defs,vcl,\
-    -DVCL_DLLIMPLEMENTATION \
+    -DVCL_DLLIMPLEMENTATION -DNOMINMAX \
     -DCUI_DLL_NAME=\"$(call gb_Library_get_runtime_filename,cui)\" \
     -DDLLPOSTFIX=$(gb_Library_DLLPOSTFIX) \
 ))

vcl/win/source/gdi/salgdi3.cxx

@@ -210,7 +210,7 @@ ImplFontAttrCache::~ImplFontAttrCache()
                 ++aIter;
             }
             // EOF Marker
-            write_lenPrefixed_uInt8s_FromOString(aCacheFile, rtl::OString(), RTL_TEXTENCODING_UTF8);
+            write_lenPrefixed_uInt8s_FromOString<sal_uInt16>(aCacheFile, rtl::OString());
         }
     }
 }