Fix the build on clang-11

Clang tidy 11 got some really neat checks that do a much better job.
Unfortunately, this, combined with the change in how std::executors has
defined how callbacks should work differently in the past, which we
picked up in 1.73, and now in theory we have recursion in a bunch of our
IO loops that we have to break manually.  In practice, this is unlikely
to matter, as there's almost a 0% chance that we go through N thousand
requests without ever starving the IO buffer.

Other changes to make this build include:
1. Adding inline on the appropriate places where declared in a header.
2. Removing an Openssl call that did nothing, as the result was
immediately overwritten.
3. Declaring the subproject dependencies as system dependencies, which
silences the clang-tidy checks for those projects.

Tested:
Code builds again, clang-tidy passes

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ic11b1002408e8ac19a17a955e9477cac6e0d7504
diff --git a/include/cors_preflight.hpp b/include/cors_preflight.hpp
index 844fd38..4bac265 100644
--- a/include/cors_preflight.hpp
+++ b/include/cors_preflight.hpp
@@ -6,7 +6,7 @@
 
 namespace cors_preflight
 {
-void requestRoutes(App& app)
+inline void requestRoutes(App& app)
 {
     BMCWEB_ROUTE(app, "<str>")
         .methods(boost::beast::http::verb::options)(