fix Windows build

after my commit 10749bbf
"remove the last of the OUString #defines in header files"

Change-Id: I0db573b59571ed859d14e5e7d5550cfa0335234d

sc/source/filter/excel/xiescher.cxx

@@ -2874,7 +2874,7 @@ OUString XclImpPictureObj::GetOleStorageName() const
     OUString aStrgName;
     if( (mbEmbedded || mbLinked) && !mbControl && (mnStorageId > 0) )
     {
-        aStrgName = mbEmbedded ? EXC_STORAGE_OLE_EMBEDDED : EXC_STORAGE_OLE_LINKED;
+        aStrgName = mbEmbedded ? OUString(EXC_STORAGE_OLE_EMBEDDED) : OUString(EXC_STORAGE_OLE_LINKED);
         static const sal_Char spcHexChars[] = "0123456789ABCDEF";
         for( sal_uInt8 nIndex = 32; nIndex > 0; nIndex -= 4 )
             aStrgName += OUString( sal_Unicode( spcHexChars[ ::extract_value< sal_uInt8 >( mnStorageId, nIndex - 4, 4 ) ] ) );