This commit adds pkgdep_rocky8.sh for installing dependencies in Rocky Linux,
and fixes compile issues (which is mostly from using different version of gcc)
We tried not to break on Ubuntu environments and we tested on our machine.

Signed-off-by: Hyunseung Park <hspark0582@gluesys.com>

Signed-off-by: Hyunseung Park <hspark0582@gluesys.com>

Installing dependencies were originally done in a new
separate file, pkgdep_rocky8.sh. As recommended in a
review comment, we have combined the two into pkgdep.sh.

We have tested new pkgdep.sh against Ubuntu 18.04,
Rocky Linux 8.6, and also CentOS Stream 8. There were
some changes to make the script also work on CentOS.
We have thought of making it also run on RHEL itself,
but since it does not provide some packages we can use
on Rocky/CentOS, we need to manually build them (too)
or use CentOS repositories. We will consider
implementing it if you desire.

Finally, some refactoring using PKGS variable.
Now it looks (hopefully/arguably) less ugly while
still not calling dnf every time.

Just copied spdk os check :)

Error occurred while installing go in rocky/CentOS since minimal install of them does not have wget and tar.
I messed up the order during combining scripts. Sorry!