Convert to standard CLI11 argument parser

This simplifies the argument parsing logic drastically and still
provides the same error handling as before.

Tested:
    Ran through unit test suite and manually verified that the command
    line functions as expected on a real BMC.

Change-Id: Ic5d69adf5359f9f64f2ada17e6a8f3242ca03e25
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/configure.ac b/configure.ac
index cd4ae00..b1e9527 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,11 @@
         AC_SUBST(GTEST_MAIN_LIBS)
     ])
 
+# We need the header only CLI library
+AC_CHECK_HEADERS([CLI/CLI.hpp], [], [
+    AC_MSG_ERROR([Could not find CLI11 CLI/CLI.hpp])
+])
+
 AC_ARG_ENABLE([oe-sdk],
     AS_HELP_STRING([--enable-oe-sdk], [Link testcases absolutely against OE SDK so they can be ran within it.])
 )