meson: add necessary subprojects

Enable the project to build outside of the OpenBMC Docker or Yocto
environments by providing subproject wrap files as necessary.  In
some cases, this requires adding additional dependencies in the meson
file due to them not currently being expressed.

Supply a .gitignore that is appropriate for a Meson project as the
current one seems to be from the time when this project used autoconf.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Iea2ae8cb9e00d2aa726800ff09b42d93efc886fc
diff --git a/subprojects/CLI11.wrap b/subprojects/CLI11.wrap
new file mode 100644
index 0000000..2e5a95b
--- /dev/null
+++ b/subprojects/CLI11.wrap
@@ -0,0 +1,6 @@
+[wrap-git]
+url = https://github.com/CLIUtils/CLI11.git
+revision = HEAD
+
+[provide]
+CLI11 = CLI11_dep