Fix Gradle builds with -Werror

[keynmol]

Problem

It turns out that under -Werror, the warning that javac emits when encountering our hacky -Arandomtimestamp=<bla> parameter causes the indexing to fail.

For an example of that, consider https://github.com/palantir/refreshable:

• Run cs launch scip-java:0.9.7 --contrib --scala 2.13.12 -- index where cs is Coursier
• Bunch of output, but the main bit is:

> Task :refreshable:compileTestJava FAILED
warning: The following options were not recognized by any processor: '[randomtimestamp]'
error: warnings found and -Werror specified
1 error
1 warning

Why do we have this -Arandomtimestamp at all?

It's there to ensure that Gradle doesn't cache the compilation results at all, as it can lead to a very frustrating experience of not seeing semanticdb files produced despite making changes to the build.

Note - gradle's clean command doesn't clean the particular cache affected by this, neither does --no-daemon option - we already have both of those in auto-indexing and caches still persist between runs without modifying javac options

Alternatives rejected

• Attempting to remove the -Werror flag from the compilation arguments

  Rejected because historically any modifications to gradle javac flags have been brittle and required hacks. Additionally, there may be builds that assert that the code is compiled with certain flags in CI, and we don't want to make any further modifications to the build
  unless it's necessary

• Making CLI argument parsing in scip-java-semanticdb more lenient to accept anything

  Rejected because we want to be strict in what arguments are being passed into the plugin, given how already difficult it is to debug compiler plugin pipeline and how much damage one can do by misspelling a parameter (i.e. putting files silently in wrong path)

• Removing this entirely and instead realying on a magical env variable

  Weakly rejected because magical env variables will require documentation for development - as opposed to a magical "always on" parameter that affects nothing but the plugin and doesn't exist anywhere but during the single gradle run for auto-indexing. The latter seems better.

Test plan

• new minimal reproduction test was added, tested on Gradle 6/7/8