Use /usr/bin/env instead of /bin/bash

[gahxke]

This PR makes it possible for NixOS and non-Linux users to build Adonis without running into problems with the shebang.

[ccuser44]

I even think sh should be used instead of bash

[ccuser44]

For better compatibility

[gahxke]

I even think sh should be used instead of bash

I guess you could use sh but

• Bash script usually #!/bin/sh If they rely on non-standard bash features, it is highly recommended to have a #!/bin/bash shebang
• In GNU/Linux, /bin/sh is Bash That depends on the distribution. It can also be dash or mksh on Debian for instance.
• In FreeBSD, /bin/sh is not bash, it's the true sh. There is a lot of sh implementations. Which one is "true"? On FreeBSD, sh is based on the Almquist shell like dash or NetBSD sh. On OpenBSD, it's based on pdksh, on many commercial Unices, it's based on ksh88 (which is the basis for the Unix/POSIX sh specification). Some ksh88-based shells and bash are the only two shells that have been certified as being a Unix compliant sh implementation (when built with the right flags and in when in the right environment).
  https://unix.stackexchange.com/questions/44785/can-i-run-bash-scripts-in-freebsd-without-modifying-them

it's still a mess on non-Linux environments, although the scripts' POSIX enough (it's just a few lines) that I don't think it'd matter that much. /usr/bin/env is way better though.