Introduce disableToolchainDetection DSL property and fix toolchain handling in BaseNativeImageOptions

[sdeleuze]

Unless I miss something, based on my tests with Liberica NIK only installed (but apply likely to GraalVM EE as well) and no GraalVM CE installation present locally (not easy because native-build-tools requires it to be built), even when applying disableToolchainDetection = true to BuildNativeImageTask implemented as part of #165 I get the following error:

> Task :nativeCompile FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':nativeCompile'.
> Error while evaluating property 'options.javaLauncher' of task ':nativeCompile'
   > Failed to query the value of property 'javaLauncher'.
      > No compatible toolchains found for request filter: {languageVersion=11, vendor=matching('GraalVM'), implementation=vendor-specific} (auto-detect true, auto-download true)

After a deeper analysis, I found that toolchain relate code in BaseNativeImageOptions need to be executed conditionally as well.

As a consequence, I propose to introduce disableToolchainDetection at DSL level (since it will be a popular option at least on Spring side for a while) to be able to just configure:

graalvmNative {
    disableToolchainDetection = true
}

And to apply it on both BaseNativeImageOptions and BuildNativeImageTask to be effective.

Be careful, to test you need to temporarily remove GraalVM CE from what is recognized by Gradle toolchain, for my tests I used Liberica NIK (available on SDKMAN) but GraalVM EE can also probably be used.

This issue is critical for Spring Native as it prevents Gradle users to use Liberica NIK which is now our default GraalVM distribution.

[melix]

I'm going to take a look, but the code you pointed at does the right thing: it's a convention so it doesn't mean that it will be used.

[sdeleuze]

I think it is used one way or another since when I remove it, #165 works as expected.

[melix]

It is used internally by Gradle to snapshot inputs, but the plugin doesn't use it, which is why it's messy. I'm working on a fix.