Jenkins pipeline can't set correct environment variables on windows

[sophia-guo]

Backslash is discarded when interpolated in groovy string.
Environment variable JAVA_BIN="$WORKSPACE/openjdkbinary/j2sdk-image/jre/bin" ( OPENJDK_TEST="$WORKSPACE/openjdk-test") can not be set up correctly.

On Windows WORKSPACE=C:\Users\jenkins\workspace\openjdk_test_x86-64_windows $WORKSPACE is interpolated as C:Usersjenkinsworkspaceopenjdk_test_x86-64_windows.

[sophia-guo]

As backward slash is an escape character for groovy String include '\'
will get compiling failure : GroovyUserScript: 1: unexpected char: '\'

Replacing ${WORKSPCE} in string is to evaluate its string representation by calling it toString() method. I believe environment variables is returned at Declarative jenkins environment section with "\" discarded. Create an issue Environment variable replacement on WINDOWS discard backslashes : https://issues.jenkins-ci.org/browse/JENKINS-44482. I have searched a little bit, there is an similar but not same one issue :https://issues.jenkins-ci.org/browse/JENKINS-31144. Seem won't fix.

For now I have two choice:

1. Hard code environment variable for windows using slashes
   JAVA_BIN='C:/Users/jenkins/workspace/openjdk_test_x86-64_windows/openjdkbinary/j2sdk-image/jre/bin'

2. Using step

withEnv(["OPENJDK_TEST=${WORKSPACE}/openjdk_test_x86-64_windows/openjdk-test"]) {
}

The second choice will require using withENV() for each stage and all relate steps have to be inside this withEnv block.