Support Kotlin DSL Gradle projects when adding/listing/removing extensions

[pschyma]

Describe the bug
The addExtension gradle task does not honor kotlin DSL build files and creates instead empty groovy DSL build configuration files: build.gradle and settings.gradle.

Expected behavior
Adding an extension should create a new entry in the dependencies block of the existing build.gradle.kts file.

Actual behavior
Nothing is added to build.gradle.kts, but instead build.gradle and settings.gradle files are created.

To Reproduce
Steps to reproduce the behavior:

1. Create a new gradle kotlin DSL project
2. Add quarkus plugin
3. Execute `./gradlew addExtension --extensions="agroal"

**Environment (please complete the following information):**
 - Output of `uname -a` or `ver`: Linux voyager 5.4.0-arch1-1 #1 SMP PREEMPT Mon, 25 Nov 2019 22:31:57 +0000 x86_64 GNU/Linux
 - Output of `java -version`: 
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-20191008104205.buildslave.jdk8u-src-tar--b07)
OpenJDK 64-Bit GraalVM CE 19.3.0 (build 25.232-b07-jvmci-19.3-b05, mixed mode)
 - GraalVM version (if different from Java): 
 - Quarkus version or git rev: 1.0.0.Final

[geoand]

Currently we don't handle build.gradle.kts at all. It would be a nice addition.

[RotBolt]

I would like to take this issue :)

[ghost]

@kaenlupus Any progress on this?

[RotBolt]

Unfortunately, no. We have to deal with other Kotlin stuff and support. Kotlin is still in experimental phase. Trying to improve the support