meson: Add missing CLI11 check and subproject support

Change-Id: I86b9116a489e61642ee27e3dbee2fcbc267d6bca
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/subprojects/cli11.wrap b/subprojects/cli11.wrap
new file mode 100644
index 0000000..407409c
--- /dev/null
+++ b/subprojects/cli11.wrap
@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://github.com/CLIUtils/CLI11
+revision = HEAD