RFR: CODETOOLS-7903604: Provide Build.java to (eventually) replace `build.sh`

[Iris Clark]

On Fri, 8 Dec 2023 23:20:37 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

> Please review a new, alternative way to download the dependencies needed to build `jtreg`.
> 
> Currently, the generally recommended way to download or otherwise find the dependencies is to use the `make/build.sh` script.  This PR provides an essentially equivalent alternative written in Java: `make/Build.java`, which is a single source file and so can be run with the standard support for running single source file programs in the Java launcher.
> 
>     old: sh make/build.sh options...
>     new: path/to/java make/Build.java options...
> 
> The configuration values are essentially the same; in particular, the default configuration values in `make/build-support/version-numbers` are exactly the same as for `build.sh`.  Configuration values may now also be given on the command-line or in a file specified on the command line. The primary configuration difference is that there is no longer support for downloading a version of JDK to build jtreg; the default is to use the same version of JDK as is used to run `Build.java` although an alternate version of JDK to build `jtreg` itself can be specified as an option to `Build.java`.
> 
> As with `build.sh`, the new `Build.java` writes and optionally executes a shell script to run `make` with variables set up to point to the local version of the dependencies. 
> 
> There is no change to the makefiles, or to the functionality of `jtreg` itself.
> 
> There are minor internal changes to the organization of the dependencies in the `build/deps` directory, and minor changes to the logging output written by the program.
> 
> The old `build.sh` and related shell files remain in place for now, but may be removed at some point in the future.

make/Build.java line 32:

> 30: #
> 31: # The program can be executed directly as a single source-file program
> 32: # by the Java launcher, using JDK 12 or later.

Just curious... why JDK 12?  I presume there's a goal to use the oldest release possible and there's a feature you need in 12?

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PR Review Comment: https://git.openjdk.org/jtreg/pull/177#discussion_r1457775933