Configure Kokoro to run CMake builds on Ubuntu.

Change-Id: I616783521bbfc21449ee3ea1a72a23a4ae27bad5
Reviewed-on: https://code-review.googlesource.com/c/re2/+/44152
Reviewed-by: Paul Wankadia <junyer@google.com>
diff --git a/kokoro/ubuntu-cmake.cfg b/kokoro/ubuntu-cmake.cfg
new file mode 100644
index 0000000..63d4f91
--- /dev/null
+++ b/kokoro/ubuntu-cmake.cfg
@@ -0,0 +1 @@
+build_file: "re2/kokoro/ubuntu-cmake.sh"
diff --git a/kokoro/ubuntu-cmake.sh b/kokoro/ubuntu-cmake.sh
new file mode 100755
index 0000000..ef4b7dc
--- /dev/null
+++ b/kokoro/ubuntu-cmake.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+set -eux
+bash git/re2/kokoro/cmake.sh
+exit $?