NullPointerException at NativeJavaCompiler when using JRE

If you use JRE instead of JDK, ToolProvider.getSystemJavaCompiler() returns null and will result in NPE later.

https://github.com/kiegroup/drools/blob/996e8f40dec9f25650dfb0457eb09bad3b1cebc7/kie-memory-compiler/src/main/java/org/kie/memorycompiler/jdknative/NativeJavaCompiler.java#L88

Probably should add a null check and throw an error message, something like "Cannot perform native java compilation: could not find the System's Java compiler. Maybe install a JDK?"

FYI)
https://groups.google.com/g/optaplanner-dev/c/2UkiCjPua5w/m/BebSTW0zCAAJ
https://stackoverflow.com/questions/2543439/null-pointer-exception-while-using-java-compiler-api/2543485#2543485
https://stackoverflow.com/questions/65682295/course-timetabling-and-conference-scheduling-examples-are-broken-in-optaplanner