Example build fails

@NorthPoleLars commented on [Mon Dec 24 2018](https://github.com/gradle-guides/creating-new-gradle-builds/issues/29)

Just installed Gradle 5.0 and following instructions on https://guides.gradle.org/creating-new-gradle-builds/.

It doesn't work as expected:

mbp-09:gradle-demo {{username}}$ ./gradlew copy
Downloading https://services.gradle.org/distributions/gradle-5.0-bin.zip <-- what caused this?
[version.txt](https://github.com/gradle-guides/creating-new-gradle-builds/files/2707643/version.txt)

............................................^Cmbp-09:gradle-demo larry.wilson$ ls
build.gradle.kts gradlew settings.gradle.kts
gradle gradlew.bat src
mbp-09:gradle-demo {{username}}$ nano build.gradle.kts
mbp-09:gradle-demo {{username}}$ ./gradlew copy
Downloading https://services.gradle.org/distributions/gradle-5.0-bin.zip
.................................................................................

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'gradle-demo'.
> Could not open cache directory 4qulew5h20dqkqz3cd88iw7f2 (/Users/{{username}}/.gradle/caches/5.0/gradle-kotlin-dsl/4qulew5h20dqkqz3cd88iw7f2).
> /Users/{{username}}/idea-projects/gradle-demo/build.gradle.kts:13:1: Unexpected `plugins` block found. Only one `plugins` block is allowed per script.

* 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

BUILD FAILED in 1m 33s
mbp-09:gradle-demo {{username}}$

[gradle-demo.zip](https://github.com/gradle-guides/creating-new-gradle-builds/files/2707640/gradle-demo.zip)

[version.txt](https://github.com/gradle-guides/creating-new-gradle-builds/files/2707644/version.txt)

Start with the example's build.gradle.kts and run ./gradlew copy using the attached gradle-demo.zip. Compare the script with the creating-new-gradle-builds guide and investigate the reported duplicate plugins block and Gradle 5.0 download behavior. Done means the documented example builds and the copy task completes without the reported configuration failure.

Written by the indexing model from the issue text.