So earlier today I had the this issues trying out forge modding (creating my own forge mod) everything was going well until I had to run the command "gradlew genIntellijRuns" and this command pops up -

To honour the JVM settings for this build a new JVM will be forked. Please consider using the daemon: https://docs.gradle.org/4.10.3/userguide/gradle_daemon.html.

FAILURE: Build failed with an exception.

* What went wrong:
Unable to get mutable Windows environment variable map

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Some more inforamtion the version i am running is 1.15.2, and the java installations i have are,

 - jdk.1.8.0_301

 - jdk-17

 -jre1.8.0_301

Some Pictures

First

second

third

1.15 is no longer supported on this forum.
Please update to a modern version of Minecraft to receive support.