The winhttp plugin is a CRL/OCSP fetcher plugin for the Windows platform. It supports fetching of CRL or OCSP information over HTTP/HTTPS URLs using the native WinHTTP API.
The plugin is disabled by default and can be enabled for Windows builds by adding
--enable-winhttpto the ./configure options.
The plugin has been introduced in strongSwan 5.2.0.
As MinGW usually does not come with a libwinhttp.dll, use a copy of winhttp.dll from Windows\System32 for a cross-platform build.