Current implementation of .git checking have some issues:
- If a kernel source being cloned using git-repo tool, especially
newer version, it will clone .git in .repo inside of the submodule
source.
- Newer kernel source changed how $(src) & $(srctree) output. In
the case of kernel 6.11 as I tested $(src) show the relative path
of the symlink in drivers/ instead of KernelSU main directory.
Which makes checking for ../.git existence comletely useless.

One idea I would like to propose is to check for the remote URL in
$(src). If the remote is correct then we can assume this is
KSU repo and then count the version (also unshallow the repo).
Here's what I did:
- Check if kernel is 6.9+ and then change $(src) accordingly.
- Print $(src) remote in verbose and check for the correct
 URL (both ssh & https).
- If correct, check if the repo is shallow by using
git rev-parse --is-shallow-repository. Unshallow if it's return true.
- Calculate version as usual.

The only drawback I can see so far is that forks will have to edit
the url in the Makefile, which I don't think it's much of an issue.

* Unmerged PR:
tiann#2102

Signed-off-by: hmtheboy154 <buingoc67@gmail.com>
Signed-off-by: Faris <rsuntk@yukiprjkt.my.id>