Integrated: 8328106: COMPARE_BUILD improvements

[Magnus Ihse Bursie]

On Wed, 13 Mar 2024 15:48:15 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> This is a collection of various improvements to `COMPARE_BUILD` I have been using lately.
> 
> * Introducing `DEBUG_CDS_ARCHIVE` make variable, which is set automatically when using `COMPARE_BUILD`. This will create a detailed log file for the `classes*.jsa` CDS archives creation, to help debug any differences in these files. It is also possible to call `make DEBUG_CDS_ARCHIVE=true` to get this functionality even without running comparisons.
> 
> * `otool` on macOS did not include all relevant information.
> 
> * We now create modern "unified" diffs using `diff -u` whenever the output is supposed to be seen by the user. For diffs that are processed by the tooling, the traditional style `>`/`<` diffs are still used.
> 
> * "Other" files are now getting symlinks as well, to facilitate debugging; and also the diff output is improved.
> 
> * Better handling of showing diffs: 
> 
>   The `-vv` argument was too verbose. To see diffs, you also were required to see redundant information about unchanged files, which spammed the log.  Now instead you can set `--diffs` to see the diffs but not unchanged files. By default, this is cut after 500 lines, but using `--diffs=full` you can get the whole diffs. Beware that this can cause logs the size of hundereds of MB!
> 
>   Now `-vv` is aliased to `-v --diffs`, and `COMPARE_BUILD` is run with `--diffs` instead of `-vv` as default.
> 
> * And finally, for some reason (merge error?) the file `compare_exceptions.sh.incl` were not properly removed before, just replaced with an emty file. This is now fixed.

This pull request has now been integrated.

Changeset: fcf746de
Author:    Magnus Ihse Bursie <ihse at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fcf746dede159905f7038d82d67806aa8afe0705
Stats:     68 lines in 5 files changed: 39 ins; 0 del; 29 mod

8328106: COMPARE_BUILD improvements

Reviewed-by: erikj

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PR: https://git.openjdk.org/jdk/pull/18279