unix: update to Linux kernel 6.9

Change-Id: Ib7bd9dabfcb8234c522ec357d32bfa3e87af53db
GitHub-Last-Rev: 4bea205
GitHub-Pull-Request: #194
Reviewed-on: https://go-review.googlesource.com/c/sys/+/585135
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Mauri de Souza Meneguzzo <mauri870@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: mauri870

unix/linux/Dockerfile

@@ -15,8 +15,8 @@ RUN apt-get update && apt-get install -y  --no-install-recommends \
 # Get the git sources. If not cached, this takes O(5 minutes).
 WORKDIR /git
 RUN git config --global advice.detachedHead false
-# Linux Kernel: Released 10 March 2024
-RUN git clone --branch v6.8 --depth 1 https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
+# Linux Kernel: Released 12 May 2024
+RUN git clone --branch v6.9 --depth 1 https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
 # GNU C library: Released 1 Feb 2023
 RUN git clone --branch release/2.37/master --depth 1 https://sourceware.org/git/glibc.git