sh function on windows hangs.
The simple workflow script is

node( windows-x64 ) {
sh 'uname -a'
}

on the windows node cygwin is installed and on path for the node user.
When run this hangs with the console output showing,

Started by user Steve Sides
[Workflow] Allocate node : Start
Running on scaab053 (Windows 2012 R2) in c:\jenkins\workspace\Workflow_HelloWorld
[Workflow] node {
[Workflow] sh
[c:\jenkins\workspace\Workflow_HelloWorld] Running shell script
...little spinning icon here....

Having to use 'bat' instead of 'sh' would block the project as numerous global functions and DSL's use this.