mesa/stretch: Remove LLVM apt repo

This is introducing flake into the build as the LLVM apt server is
unstable, and the packages are not substantially different from the
main debian stretch repo, so remove the dependency entierly.

BUG=none
TEST=Ran docker container locally

Change-Id: Ifae384582c8eb77e73138b9f114b48e56d340daa
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/containers/cros-container-guest-tools/+/2190093
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Tested-by: Fergus Dall <sidereal@google.com>
diff --git a/mesa/stretch/.pbuilder/hooks/G05llvm b/mesa/stretch/.pbuilder/hooks/G05llvm
deleted file mode 100755
index 4123fce..0000000
--- a/mesa/stretch/.pbuilder/hooks/G05llvm
+++ /dev/null
@@ -1,20 +0,0 @@
-# Copyright 2019 The Chromium OS Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-# Add llvm packages necesary for mesa.
-
-echo HOOK: add llvm dependencies
-
-apt-get install -y apt-utils apt-transport-https ca-certificates
-tee -a /etc/apt/sources.list <<EOF
-deb http://apt.llvm.org/stretch/ llvm-toolchain-stretch-7 main
-deb-src http://apt.llvm.org/stretch/ llvm-toolchain-stretch-7 main
-EOF
-apt-get update
-apt-get install -y --allow-unauthenticated \
-    llvm-7 \
-    llvm-7-dev \
-    libclang-7-dev \
-    libclang-common-7-dev \
-    clang-7
diff --git a/mesa/stretch/Dockerfile b/mesa/stretch/Dockerfile
index 2bfac39..d8ad572 100644
--- a/mesa/stretch/Dockerfile
+++ b/mesa/stretch/Dockerfile
@@ -25,7 +25,7 @@
 ENV DISTRIBUTION=stretch-backports
 ENV ARTIFACTS=/artifacts
 
-COPY .gbp.conf .pbuilderrc llvm-keyring.gpg  /root/
+COPY .gbp.conf .pbuilderrc  /root/
 COPY .pbuilder /root/.pbuilder/
 COPY *.sh /scratch/
 
diff --git a/mesa/stretch/README.md b/mesa/stretch/README.md
index 2c65c5e..32605e3 100644
--- a/mesa/stretch/README.md
+++ b/mesa/stretch/README.md
@@ -120,14 +120,6 @@
 The owner of the tarball must be set to `chromeos-vm-ci-read-write` to
 allows Kokoro to have access to it.
 
-## LLVM Keyring
-The LLVM keyring was generated with:
-```sh
-wget https://apt.llvm.org/llvm-snapshot.gpg.key
-gpg --no-default-keyring --keyring ./llvm-tmp.gpg --import llvm-snapshot.gpg.key
-gpg --keyring ./llvm-tmp.gpg --export --output llvm-keyring.gpg
-```
-
 ## Versioning
 The Chrome OS releases are often coming from ToT and do not match released
 or even branched mesa builds.  Pre-releases will be numbered in a format such
diff --git a/mesa/stretch/llvm-keyring.gpg b/mesa/stretch/llvm-keyring.gpg
deleted file mode 100644
index 2b451a6..0000000
--- a/mesa/stretch/llvm-keyring.gpg
+++ /dev/null
Binary files differ
diff --git a/mesa/stretch/setupchroot.sh b/mesa/stretch/setupchroot.sh
index e96b923..b63a454 100755
--- a/mesa/stretch/setupchroot.sh
+++ b/mesa/stretch/setupchroot.sh
@@ -18,8 +18,7 @@
             DIST="${DISTRIBUTION}" ARCH="${arch}" git-pbuilder create \
                 --mirror http://deb.debian.org/debian \
                 --debootstrapopts \
-                    --keyring="/usr/share/keyrings/debian-archive-keyring.gpg" \
-                --keyring="${HOME}/llvm-keyring.gpg"
+                    --keyring="/usr/share/keyrings/debian-archive-keyring.gpg"
         fi
     done
 }