Add support for 'Mach-O 64-bit dynamically linked shared library arm64'

What's the problem (or question)?

Add support for Mach-O 64-bit dynamically linked shared library arm64 (de)compression.

What should have happened?

I know that #57 and #219 added " Mach-O 64-bit executable x86_64" and "Mach-O 64-bit dynamically linked shared library x86_64".

I can also compress the plugin mentioned in #219 sucessfully. But I can't compress the Mach-O 64-bit dynamically linked shared library arm64 file.

The follow is the error:

$ ./src/upx.out /Users/Desktop/App
                       Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX git-642829  Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 24th 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
upx.out: /Users/Desktop/App: UnknownExecutableFormatException

Packed 0 files.

WARNING: this is an unstable beta version - use for testing only! Really.

Here is my file: App.zip

Do you have an idea for a solution?

How can we reproduce the issue?

1. download App.zip
2. unzip the App.zip
3. upx app

Please tell us details about your environment.

• UPX version used (upx --version): upx 4.0.0-git-6428292477e0 (devel branch)
• Host Operating System and version:macOS Catalina 10.15.5
• Host CPU architecture:x86_64
• Target Operating System and version:iOS
• Target CPU architecture:arm64