[FEATURE] Arch Linux installation script (create .pkg.tar.xz archive or install directly)

[fandango96]

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Add installation script for Arch Linux based distributions.

Steps to test this out (on an Arch Linux based distribution):
$ cd package_creators/
$ ./arch.sh

There is an option to do 2 things (install directly or create the .pkg.tar.xz archive for distribution purposes without installing on host machine).

Tested on
Kernel : Linux 4.4.48-1-MANJARO (x86_64)
C Library : GNU C Library version 2.24 (stable)
Default C Compiler : GNU C Compiler version 6.3.1 20170109 (GCC)
Distribution : Manjaro Linux

Resolves sub-part of Issue #678

[rkuchumov]

1. I've got ./arch.sh:read:8: -p: no coprocess. (I fixed it by changing #!/bin/sh to bash, but you should check it)
2. There may be no sudo in the system
3. When ./autogen.sh or ./tarball.sh fails arch.sh still asks me to install the package.
4. When I answer anything but n or N to the prompt, it still install the package. But default behavior everywhere in this case is to exit

[fandango96]

Thanks for the review.

1. Changed to use bash as the shell
2. Use 'su' instead of 'sudo' now
3. Fixed; now if a command fails, the script won't continue
4. I was just emulating the default behaviour of pacman / makepkg - Y is the default there. However, I've now changed the prompt within arch.sh to have N as the default.

[rkuchumov]

Use 'su' instead of 'sudo' now

But when the system has sudo, you should use it :) Usually scripts try sudo at first, (which asks user password), and if they fail to find it, they use su (which asks root password). You should either implement this logic or just remove installation step and let user do it.

Don't forget to add .gitignore, to update docs/CHANGES.TXT and to add instructions to README.md

[fandango96]

Done - 'sudo' is used if available; fallback to 'su'. Also, updated the mentioned files.

[rkuchumov]

Ok, thanks.
It can be merged.