RFR: 8313374: --enable-ccache's CCACHE_BASEDIR breaks builds [v2]

[David Holmes]

On Mon, 31 Jul 2023 05:06:39 GMT, Jan Kratochvil <jkratochvil at openjdk.org> wrote:

>> I see, I don't think we have to keep CCACHE_BASEDIR if it is not required, but we should test it to see how the build reacts to such a change, since it does change the behaviour of ccache which is a little bit nerve wracking. I unfortunately cannot see the bug either, perhaps either David or @erikj79 could help with why both options were implemented this way
>
>> I see, I don't think we have to keep CCACHE_BASEDIR if it is not required,
> 
> BTW `CCACHE_BASEDIR` is a caching improvement - without it builds in different directories never share the cache. Some existing `ccache` users may find the `CCACHE_BASEDIR` removal as a regresson. Although I doubt anyone is using `ccache` with OpenJDK as it has been a PITA without working dependencies.

@jankratochvil See the comments here: 

https://github.com/openjdk/jdk/blob/eaa42e853dbe45c5dd26f75d0b3c242ebebdd286/make/autoconf/flags-cflags.m4#L821

and before the change you made in NativeCompilation.gmk to understand why this is done.

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PR Comment: https://git.openjdk.org/jdk/pull/15080#issuecomment-1657606622