Upgrade commons-compress to 1.18 and tukaani xz to 1.8

This version of commons-compress includes fixes for CVE-2018-1324 [1]
and CVE-2018-11771 [2].

Also update tukaani xz to 1.8, which is the version used by
commons-compress 1.18.

[1] https://nvd.nist.gov/vuln/detail/CVE-2018-1324
[2] https://nvd.nist.gov/vuln/detail/CVE-2018-11771

Change-Id: I4bf8ccc239445f20794844e6ea96005d7c8b9c77
diff --git a/tools/nongoogle.bzl b/tools/nongoogle.bzl
index 2e84717..6788bc9 100644
--- a/tools/nongoogle.bzl
+++ b/tools/nongoogle.bzl
@@ -11,6 +11,6 @@
     # Transitive dependency of commons-compress
     maven_jar(
         name = "tukaani-xz",
-        artifact = "org.tukaani:xz:1.6",
-        sha1 = "05b6f921f1810bdf90e25471968f741f87168b64",
+        artifact = "org.tukaani:xz:1.8",
+        sha1 = "c4f7d054303948eb6a4066194253886c8af07128",
     )