Allow building with boost 1.87

Boost for whatever reason added nodiscard on boost::asio::spawn.  Long
term someone likely needs to move this coroutine stuff over to c++20
coroutines, but for now, put in maybe_unused where appropriate.

Change-Id: I59d1851476ed29290e260ba31ef1fe7508b3f441
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/ipmid-new.cpp b/ipmid-new.cpp
index 1bb8934..e8cc2f1 100644
--- a/ipmid-new.cpp
+++ b/ipmid-new.cpp
@@ -21,6 +21,7 @@
 
 #include <boost/algorithm/string.hpp>
 #include <boost/asio/io_context.hpp>
+#include <boost/asio/spawn.hpp>
 #include <host-cmd-manager.hpp>
 #include <ipmid-host/cmd.hpp>
 #include <ipmid/api.hpp>
@@ -764,7 +765,7 @@
 {
     // make a copy so the next two moves don't wreak havoc on the stack
     sdbusplus::message_t b{m};
-    boost::asio::spawn(
+    (void)boost::asio::spawn(
         *getIoContext(),
         [b = std::move(b)](boost::asio::yield_context yield) {
             sdbusplus::message_t m{std::move(b)};