Use stable kernels

Distros are more likely to be following stable than Linus's tree. So use
this instead. These also get fixes (build or otherwise) over time.

Author: danobi

KERNELS

@@ -1,4 +1,4 @@
-v5.15
-v6.1
-v6.6
-v6.12
+v5.15.177
+v6.1.128
+v6.6.75
+v6.12.12

docker/Dockerfile.kernel

@@ -23,7 +23,7 @@ RUN apk update && apk add \
 
 WORKDIR /
 
-ARG KERNEL_REPO=https://github.com/torvalds/linux.git
+ARG KERNEL_REPO=https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
 ARG KERNEL_TAG
 
 RUN git clone --depth 1 ${KERNEL_REPO} linux --branch ${KERNEL_TAG}