Bug: bashism in configure

[Euro20179]

Problem

On line 2866 it uses ${with_gtk:0:1} which isn't posix, which is ok but, it would be better to have the shebang be #!/bin/bash or change this to a posix alternative.

The reason I am making this is because my /bin/sh is dash, which is also the default on ubuntu/debian.

Potential Solution

GTK_API="$(printf "%s" "$with_gtk" | grep '.' | sed 1q)"

Reason Im not making a pull request

I'm lazy.

Edit: seems there is more on line 18446, and possibly more.

[Keruspe]

configure is going away in favor of meson anyways