fix: bytecode version unspecified & NPE and trySetAccessible method does not exist on Android

[naijun0403]

Fixes #1634

[gbrail]

Thanks -- I am going to open a PR soon that uses the "Errorprone" plugin to help detect these kinds of things proactively, but TBH nothing is going to be really permanently better until we have some way to do some sort of Android smoke test as part of the build, or somewhere in GitHub. Do you have any idea how other projects might handle this?

In the meantime, I'd love to understand better why the change to the class file writing is necessary. I'd be even happier if we could find some way to write a test for it -- any ideas?

[naijun0403]

Thank you for your feedback!

Regarding testing:
I'm aware that the nowinandroid repository uses Android emulators for testing. However, my knowledge of testing methodologies is limited, so I can't provide comprehensive suggestions for alternative testing methods.

Reason for modifying ClassFileWriter.java:
The modification was necessary due to Android's unique runtime environment. Android doesn't use the JVM, so .class files are not included in the app. Consequently, in the source code, inputStream was always null, leading to a NPE that prevented the entire engine from functioning.

Changes made:

1. I added a null check for inputStream.
2. If inputStream is null, I substitute default minor and major version values (retrieved from a previous commit) to ensure null safety in subsequent operations.

This approach aims to prevent NPE and maintain the engine's functionality in the Android environment.

[rPraml]

I stumbled upon this place in #1575 (which probably will cause merge conflicts)
I'm wondering, if we should replace this with VMBridge.instance.tryToMakeAccessible(method)
which will effectively call this code: https://github.com/mozilla/rhino/blob/master/rhino/src/main/java/org/mozilla/javascript/jdk18/VMBridge_jdk18.java#L57

[naijun0403]

Maybe that's a good idea. I guess it will work on Android too.

[gbrail]

Thanks! Resolved the conflict and merged manually.