JavaNativeFoundation is hard to build on arm64

[cbfiddle]

I found it a bit challenging to build the framework on my arm64 system.

1. I had to create a symbolic link at openjdk to the apple jdk. (Not documented?)
2. I had to install and select Xcode 13.4.1 to build with the minimum deployment target of 10.10.
3. I had to explicitly run the build script on Rosetta: commandLine("arch", "-x86_64", "/bin/bash", "build_jnf.sh"). Perhaps it should have worked automatically, but there may be a bug in the arch command.

[cbfiddle]

I have a better fix for problem #3. The build script was incorrect.

[weisJ]

1. I had to create a symbolic link at openjdk to the apple jdk. (Not documented?)

The openjdk is a git submodule which you also have to check out. Please don't delete the submodule in #5 as it will break the build.

2. I had to install and select Xcode 13.4.1 to build with the minimum deployment target of 10.10.

The deployment target is controlled by the openjdk code. The files would need to be copied over and the build adjusted to fix this. Technically possible as JNF isn't maintained by the jdk anymore anyway, so there won't be any changes from the jdk side of things.

[cbfiddle]

I have replaced the symlink with the sources.
I have added a second build script that uses command tools directly instead of running xcode-build. This allows setting the minimum deployment to 10.10. It no longer needs to be run on Rosetta. (I also fixed a problem in the original build script related to running on Rosette.)