Find attention gpio rather than hard code value

Find the attention gpio by line-name (checkstop) rather than by
chip and pin number. This allows the attention handler to work on
platforms with the attention signal tied to different GPIO's.

Also fixed issue of pdbg targets not getting initialized when
attention handler is built to run in no-listener mode (build option
nlmode, the default for now).

Added/changed a few trace messages to aid in future debugging.

Changed build to not link to libpdbg using "whole-archive" strategy
as it does not seem to be needed anymore.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: Id355ce03b716cb0c86bc3418264295dcc60aabef
diff --git a/main_nl.cpp b/main_nl.cpp
index 2725860..31017ea 100644
--- a/main_nl.cpp
+++ b/main_nl.cpp
@@ -1,3 +1,5 @@
+#include <libpdbg.h>
+
 #include <analyzer/analyzer_main.hpp>
 #include <attn/attn_config.hpp>
 #include <attn/attn_main.hpp>
@@ -42,6 +44,8 @@
             {
                 attn::Config attnConfig; // default config
 
+                pdbg_targets_init(nullptr); // initialize pdbg targets
+
                 attn::attnDaemon(&attnConfig); // start daemon
             }
         }