The only present test case rebuilt, installed and booted the kernel.
Now let's make the install and boot steps optional, just on explicit
request. Skipping these steps will be the default behaviour, at least
for now.
You can override the default by setting variable "JUST_BUILD" in the
environment the test runs in. The variable defaults to "yes" which
means the test will just build the kernel. If you use JUST_BUILD=no
(or JUST_BUILD=false or JUST_BUILD=0) then the test will not only
build but install and boot the kernel, too.
Note that the acceptable values of JUST_BUILD are case insensitive.
* Remove code related to RHEL versions and not interesting in Fedora.
* Remove or simplify some architecture-specific code because Fedora CI
aims at x86_64 only.
* Remove some older and commented out experiments.
Sanity/rebuild-kernel-and-reboot is imported from RHEL's
tests/binutils/Sanity/rebuild-kernel-and-reboot (as of commit c5bc77c).
It needs some adaptations first before running in Fedora.
