debuggerd: diagnostics for dumps that are guaranteed to fail.

Print diagnostics when the user requests a dump that is guaranteed to
fail, such as trying to dump a process you can't send a signal to.

Bug: http://b/63008395
Change-Id: I5c6bf2a5751f858e0534990b8d2ab6932eb9f11d
Test: manually tested
diff --git a/debuggerd/Android.bp b/debuggerd/Android.bp
index 5565cfd..f993820 100644
--- a/debuggerd/Android.bp
+++ b/debuggerd/Android.bp
@@ -274,6 +274,7 @@
         "libbase",
         "libdebuggerd_client",
         "liblog",
+        "libprocinfo",
         "libselinux",
     ],