[code-reflection] Integrated: Git use cmake jextract in maven

[Gary Frost]

Previously we added cmake artifacts (CMakeFiles.txt) to opencl, opengl and cuda subdirs in extractions. 

Here we added the resulting java source files to the maven pom hierarchy. 

Upshot of which, we (on Mac with OpenCL) use maven to build everything.. well nearly, we still need to manually run cmake

So this should work

bash maven-build.bash 
java @hat/run ffi-opencl nbody

Note that the maven build bash script actually has a new step to run cmake on extractions dir


echo We need to run cmake in extractions dir first 
pushd extractions
rm -rf cmake-build-debug
cmake -B  cmake-build-debug
cmake --build cmake-build-debug --target extract 
popd
echo Now we can use maven 
mvn -e clean compile package install
``` 

I will remove this and put it into the maven build, when I grok how to add a source generator to maven.

-------------

Commit messages:
 - Arrange for maven-build.bash to call cmake in extractions dir
 - Allow maven to use cmake extracted files

Changes: https://git.openjdk.org/babylon/pull/400/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=400&range=00
  Stats: 171 lines in 10 files changed: 150 ins; 2 del; 19 mod
  Patch: https://git.openjdk.org/babylon/pull/400.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/400/head:pull/400

PR: https://git.openjdk.org/babylon/pull/400