[ci] Add a CI template for package manager calls.

Also introduces apt-requirements.txt, so there is One Source of Truth
for apt-get packages.

Signed-off-by: Miguel Young de la Sota <mcyoung@google.com>
diff --git a/apt-requirements.txt b/apt-requirements.txt
new file mode 100644
index 0000000..0aadd6a
--- /dev/null
+++ b/apt-requirements.txt
@@ -0,0 +1,28 @@
+# Copyright lowRISC contributors.
+# Licensed under the Apache License, Version 2.0, see LICENSE for details.
+# SPDX-License-Identifier: Apache-2.0
+
+# Keep sorted.
+autoconf
+bison
+build-essential
+clang-format
+curl
+flex
+g++
+git
+libelf1
+libelf-dev
+libftdi1-2
+libftdi1-dev
+libssl-dev
+libusb-1.0
+make
+ninja-build
+pkgconf
+python3
+python3-pip
+python3-setuptools
+srecord
+tree
+zlib1g-dev