Fix/wrong architecture string on appimagetool arch/1114

[azubieta]

Allows using armhf and aarch64 as architecture names on appimagetool. Doesn't remove the old names ("arm", "arm_aarch64") to avoid breaking scripts of possible users.

Closes #1114

[probonopd]

Why do you want to hardcode pathToMksquashfs = "/usr/bin/mksquashfs";?

I think this breaks bundling mksquashfs privately?

[azubieta]

Why do you want to hardcode

Ups, that's wrong. It should be fixed now

[azubieta]

Should I proceed with the merge?

[probonopd]

Lgtm. @TheAssassin?

[probonopd]

Is this still a thing? @TheAssassin wdyt?

[hyh19962008]

I totally agreed "arm_aarch64" is misleading, and the command-line help message doesn't provide this information, you have to look into the source code to find it.