treewide: Remove some bashism

[SvenRoederer]

This removes some non POSIX extensions from the shell-scripts, as already done in d6ac8ca. It targets "[[" and "==".

[adschm]

For commit messages like "[[ is a bash-extension for test the ash-implementation is in fully compatible." I think it makes more sense to just put the "[[" in standard quotes.

[neheb]

If bashisms are to be removed, it makes sense to change the top shebang to point to /bin/sh as dash is faster than bash.

edit: A moot point as these do not run on the host but it's still correct to add a shebang.

[adschm]

@SvenRoederer Regarding "-a":
https://patchwork.ozlabs.org/patch/1216221/

[SvenRoederer]

@neheb I added the shebang to the files I edited. The scripts I edited are only running on the target-board, so /bin/sh links to busyboy-ash, right?

@adrianschmutzler Regarding "-a": see 01c84b4

[adschm]

@SvenRoederer I think it will be more efficient if you already provide properly formatted patches in the first place. That will allow me to pick what's ready (or looks correct) right away. Currently, I would have to look at rather "trivial" patches several times, but I do not think this will benefit so much from having it pre-reviewed.
However, feel free to stick to your current plan if you prefer.

[adschm]

Ping.

[SvenRoederer]

@adrianschmutzler commits db23f92 , 38bebf5 , aeb858d , 0cc2d7c can be cherry-picked.

The commits related to igmpproxy should be reviewed.

[adschm]

Note that the author of your patches (From:) does not match your SOB. I corrected that manually for those patches already merged, but please take care of future patches yourself.

[SvenRoederer]

Adding the shebang was based on this comment #2647 (comment).

I changed my github settings, which hopefully improves the "From:" header.

[SvenRoederer]

@adrianschmutzler I just got a ping for this PR and reworked commits according to your comments. I also tested the change of the 2 commit to give the same results as the original.

[adschm]

Hmm, just had another look and I still don't like it. The first commit tells to change brackets, but also changes &&/-a and -z/-n, only to have it changed again in the second commit.

Please separate these changes properly. Despite, be aware that I'm treating this low-priority as it's cosmetic.

Thanks for your work, however.

[adschm]

I've squashed the two patches together with a slightly modified message and will merge them later today.

[SvenRoederer]

Thanks for taking care.... I had it on my list with a list with a low priority ...