Sandbox libxml2 and switch clang to zstd compression

When trying to execute clang on a very very fresh Debian image, it can't
find libxml2.  Sandbox that too.

While we are here, zstd images extract faster than xz.  Switch over.

Change-Id: Ia196ae49223b488f5eabe28b67e6f274b3072795
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/debian/clang_amd64.bzl b/debian/clang_amd64.bzl
new file mode 100644
index 0000000..dfa7612
--- /dev/null
+++ b/debian/clang_amd64.bzl
@@ -0,0 +1,6 @@
+files = {
+    "libicu72_72.1-3_amd64.deb": "e239c1c9f52bee0ff627f291552d63691b765ec7c5cdf6de7c7ae4dec0275857",
+    "libstdc++6_12.2.0-14_amd64.deb": "9b1b269020cec6aced3b39f096f7b67edd1f0d4ab24f412cb6506d0800e19cbf",
+    "libtinfo5_6.4-4_amd64.deb": "dd347f794e651039e7b4c391f86c674fed7f415b3dca6b0937beb0d470f09c1a",
+    "libxml2_2.9.14+dfsg-1.3~deb12u1_amd64.deb": "35b76cb7038fc1c940204a4f05f33ffb79d027353ce469397d9adcf8f9b3e1a7",
+}