Bugfix: Replace bashisms with standard sh to fix build on non-BASH systems

[luke-jr]

Note: I have not actually tested this on a non-BASH system yet.

Downstream Gentoo bug: https://bugs.gentoo.org/show_bug.cgi?id=524332

[theuni]

ACK in principle. As you said on IRC, I'd like to have travis testing for this. Shouldn't be too hard to spawn in a new shell and export a few things as needed.

One request though.. please split into 3 commits: build/tests/gitian, that way we can backport more easily if needed.

[luke-jr]

Split

[theuni]

@luke-jr Please see #5040 and grab the commit from there if you agree with it (I'll close that PR).

If that is green, ACK.

[theuni]

In case it's non-obvious to anyone reading after-the-fact:

This PR adds fixes for shell-scripts that needlessly used bashisms. There was previously no test for these. #5040 introduced a test, and the build failed as expected. This PR fixes the scripts and adds the test from #5040. The fact that it's green means that they're confirmed fixed.

ACK.

[gmaxwell]

utACK.

[laanwj]

Not meaning to depreciate this pull, but is there really no modern non-bash alternative to uglyness like

if test x$use_pkgconfig = x; then

I remember, from maybe 20 years ago, that constructions like that were used for compatibility with some shell from the 80's. Hasn't really anything changed on that front?

[luke-jr]

@laanwj I'm pretty sure

if test "$use_pkgconfig" = ""; then

is fine in most shells, but when the entire purpose of a configure script is portability, it makes sense to use the most portable code.

[laanwj]

It's just so stupid to have to add a dummy string to do a string comparison, as if it's some amazing new thing. In other places we also have limits on how far we go back with regard to compatibility.

Anyhow, I was just asking. For anything worthwhile (that is actually meant to be reviewed) we should be using Python, not shellscript.

utACK.

[Michagogo]

Um, why did we make the changes within the gitian build scripts? Those, by definition, run on Ubuntu 12.04, and with bash, unless I'm missing something. I just checked gitian's source, and the build script has a hard-coded #!/bin/bash, as well as the fact that the actual command run is on-target setarch #{@arches[arch]} bash -x < var/build-script > var/build.log 2>&1

[luke-jr]

Better to use standards?

[Michagogo]

It just seems weird to me to make it ugly in the name of compatibility/reducing bashisms, in a script that will only ever be run by bash.

[laanwj]

@Michagogo Agreed. Wouldn't have been needed for the gitian descriptors as it forces bash. It's just the basic build system that needs to be compatible between shells. @theuni We could revert this with #4727, which completely overhauls the gitian descriptors anyway.

[theuni]

Yea, all of the above is fine by me. I didn't argue it because they should be obsoleted soon anyway, as you said.