new jextract builds

[Maurizio Cimadamore]

Hi,
we have refreshed the jextract binary builds with some small updates:

* put the jextract launcher into a "bin" folder in the jextract root 
folder [1]
* reduce the size of the Linux downloadable, by removing duplicate 
versions of libclang [2]
* tweak the build to make the jextract launcher executable [also in 1]
* tweak the build to bundle an OpenJDK runtime [3]

You can find the binaries in the usual place:

https://jdk.java.net/jextract/

Cheers
Maurizio

[1] - https://github.com/openjdk/jextract/pull/247
[2] - https://github.com/openjdk/jextract/pull/246
[3] - https://mail.openjdk.org/pipermail/jextract-dev/2024-May/001709.html