Fix associates compile classpath

[rbeazleyspot]

This is a (surprisingly) small PR to resolve #1250.

Any friends mentioned were not added to the classpath so KotlinBuilder now adds them and it keeps the compilation units friends close by adding them to the head of the classpath

Any friends jars that were aded were effectively just the ABI jars so associates.bzl now uses the class jars (which contain any internal declarations)

---

I had a hard time (ie failed) writing a test for this, i can only be sure the existing mechanism works ok.

Locally i redefined the tool chain to enable the relevant experimental options

define_kt_toolchain(
        name = "default_toolchain",
        experimental_remove_private_classes_in_abi_jars = True,
        experimental_treat_internal_as_private_in_abi_jars = True,
        experimental_use_abi_jars = True,
        language_version = "2.1",
        api_version = "2.1",
    )

with these in place the basic associates test fails, applying these commits makes it pass

an integration test could be added once a release is cut maybe?

[rbeazleyspot]

well it looks like the same code fails on CI :)

so i guess ill look into this

-- edit
Still worth getting your feedback on this whilst i scratch my head

[rbeazleyspot]

rookie mistake, not of course adding the associates java_outputs as an input to the compilation action, thanks for the help debugging @gabrielborglund

[rbeazleyspot]

I've tried to work out why the integration tests are failing, no idea ! sorry :/

[rbeazleyspot]

FYI, i believe with this change in place and considering a build graph that looks like this:

A - deps=[B], associates=[C]
B - deps=[C, D]

the compilation class path will look like this

C-full-runtime.jar (Collected from friends)
B-abi.jar (plus stdlib etc)
C-abi.jar (Collected from the transitive deps)
D.abi.jar

which is a change from

B-abi.jar (plus stdlib etc)
C-abi.jar (Collected from the transitive deps)
D.abi.jar

.... its possible a different angle could be taken and when the java_info for the associate_deps is collected here in compile.bzl

then it could be massaged to drop any ABI jars ie set compile_jar to output_jar