Add support for arm64

[krzysdz]

Describe what you did

Added proper version of node.js for arm64 arch

How you did it

Set arch to arm64 (used in URL's in Node.js downloads) if uname returns aarch64 as architecture

How to verify it doesn't affect the functionality of n

Install Node.js on a system with other architecture and check whether it still works (it should)

If this solves an issue, please include the output of issue that had problems and then the fixed output from the same command.

Problem 1

Before - versions 10.0.0 (and higher):

krzys@localhost:~/node-v8.11.2-linux-arm64$ sudo env "PATH=$PATH" n 10.0.0

install : node-v10.0.0

Error: invalid version 10.0.0

After:

krzys@localhost:~/node-v8.11.2-linux-arm64$ sudo env "PATH=$PATH" n 10.0.0

install : node-v10.0.0
  mkdir : /usr/local/n/versions/node/10.0.0
  fetch : https://nodejs.org/dist/v10.0.0/node-v10.0.0-linux-arm64.tar.gz

installed : v10.0.0

Problem 2

Before - errors during installation (due to incorrect architectute):

krzys@localhost:~/node-v8.11.2-linux-arm64$ sudo env "PATH=$PATH" n lts

install : node-v8.11.2
  mkdir : /usr/local/n/versions/node/8.11.2
  fetch : https://nodejs.org/dist/v8.11.2/node-v8.11.2-linux-x86.tar.gz

/home/krzys/node-v8.11.2-linux-arm64/bin/n: linia 583: /usr/local/bin/node: nie można uruchomić pliku binarnego: Błędny format pliku wykonywalnego
installed :

The error message says that the executable cannot be executed due to incorrect executable format

After:

krzys@localhost:~/node-v8.11.2-linux-arm64$ sudo env "PATH=$PATH" n lts

   install : node-v8.11.2
   mkdir : /usr/local/n/versions/node/8.11.2
     fetch : https://nodejs.org/dist/v8.11.2/node-v8.11.2-linux-arm64.tar.gz

installed : v8.11.2

Place description for the changelog in PR so we can tally all changes for any future release

Fix Node.js installation/upgrade for systems using arm64 architecture

[krzysdz]

Duplicate of #494