Print out warning only if platform is not Ubuntu and make build directory relative to where build starts

[linh2931]

#363 reports pinned_build.sh always prints "Currently only supporting Ubuntu based builds. Proceed at your own risk.", even on Ubuntu platform.

#364 reports the build directory is made relative to the dependency directory; it should have been relative to the directory where the script starts.

This PR fixes those two issues.

[spoonincode]

fwiw this may not yield expected behavior when running ubuntu in a container. Also, how safe is it for uname -v to not be in quotes here. Locally I see spaces in that

$ uname -v
#1 SMP PREEMPT_DYNAMIC Thu, 09 Jun 2022 16:14:10 +0000

[matthewdarwin]

I was expecting something more like:

#!/bin/sh

if [ -e /etc/os-release ]
then
        . /etc/os-release
fi

echo $ID

[linh2931]

Thanks Matt. I will add quotes there.

I was testing inside a Ubuntu container built on VirtualBox on my PC

uname -v
#49~20.04.1-Ubuntu SMP Wed May 18 18:44:28 UTC 2022

I will change to do uname -a to be safe.

[matthewdarwin]

This will not work. I am running a Ubuntu lxc container on a debian host. uname -a shows Debian. It is not debian (only the kernel is Debian).

[linh2931]

Thanks @matthewdarwin. I have changed to use os-release and provide specific reason when a build is not support.

[spoonincode]

This looks good but we'll want the change in 3.1 so based on our branch strategy this change needs to be PRed to the 3.1 branch first. (sorry for the unfortunate timing!) You'll need to open a new PR with these changes based on the 3.1 release branch.

[linh2931]

Do release/3.1.x PR #487 first. And then merge that to main. Close this one.