RFR: 8294368: Java incremental builds broken on Windows after JDK-8293116

[Daniel Jeliński]

On Tue, 4 Oct 2022 16:19:24 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> This patch fixes incremental builds on Windows.
> 
> There are 2 parts to this:
> 1. the build system needs to run the paths in the modified file list through fixpath. I've added a `convert` mode to `fixpath.sh` for that. There's an extra target for generating the file with fixed paths. On non-windows platforms this is just a simple `cp` of the file.
> 2. the dependency plugin of `javac` was using string-based path comparison. But, the paths fed by the build system and the paths used internally by javac could be in slightly different formats, meaning that files were not detected properly as changed. I switched to `Path`-based comparison instead and that fixes the issue.
> 
> Testing:
> tested this manually by doing the following:
> 1. `make clean`
> 2. `make images`
> 3. put garbage in one of the files in `java.base`
> 4. `make images` (incremental)
> 5. verify that the build reported an error
> 6. verify the contents of `<build>\jdk\modules\java.base_the.java.base_batch.modfiles.fixed`
> 7. revert the changes of 3, and do the same for another file
> 8. `make images` (incremental)
> 9. verify that the build reported an error
> 10. verify the contents of `<build>\jdk\modules\java.base_the.java.base_batch.modfiles.fixed`
> 11. remove garbage from file modified by 9 again
> 12. `make images` (incremental)
> 13. verify that build succeeds as in 2
> 
> I've tested the build on Windows and Linux (WSL) using the above steps.

Also verified that:
- changes to public interface trigger full recompilation
- changes that do not affect public interface cause minimal recompilation.

This was on Cygwin. LGTM!

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Marked as reviewed by djelinski (Committer).

PR: https://git.openjdk.org/jdk/pull/10560