We have a landscape, where only a subset of our windows jenkins slaves have cygwin installed.
On the slaves without cygwin, the jenkins cygpath plugin gets an error. Note that also happens on steps, that are not related to cygwin, as can be seend in the error appended at the end - in that case invocation of a maven task.

Suggestion is NOT to fail, and simply do nothing, passing the commands thru without any modifications.

Will attach a patch that provides a solution.

FATAL: command execution failed
hudson.util.IOException2: Failed to locate Cygwin installation. Is Cygwin installed?
at hudson.plugins.cygpath.CygpathLauncherDecorator$GetCygpathTask.getCygwinRoot(CygpathLauncherDecorator.java:138)
at hudson.plugins.cygpath.CygpathLauncherDecorator$GetCygpathTask.call(CygpathLauncherDecorator.java:142)
at hudson.plugins.cygpath.CygpathLauncherDecorator$GetCygpathTask.call(CygpathLauncherDecorator.java:112)
at hudson.remoting.UserRequest.perform(UserRequest.java:118)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:326)
at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at hudson.remoting.Engine$1$1.run(Engine.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: hudson.util.jna.JnaException: Win32 error: 2 - null
at hudson.util.jna.RegistryKey.check(RegistryKey.java:124)
at hudson.util.jna.RegistryKey.open(RegistryKey.java:223)
at hudson.util.jna.RegistryKey.openReadonly(RegistryKey.java:218)
at hudson.plugins.cygpath.CygpathLauncherDecorator$GetCygpathTask.getCygwinRoot(CygpathLauncherDecorator.java:127)
... 11 more
Build step 'Invoke top-level Maven targets' marked build as failure ... 11 more