RFR: Make Serviceability Agent attach functionality optional

[Mikael Vidstedt]

The Serviceability Agent (aka. SA) has functionality to attach to running processes forcefully/without the cooperation of the VM, allowing “live” debugging even when the processes is stuck. On linux the implementation relies on the functionality provided by the thread_db.h header file.

musl doesn’t support thread_db.h (or any other thread debugging library for that sake). This patch makes the inclusion of the attach/live debugging support optional, and only includes it if the thread_db.h header file is available.

Note that the core debugging functionality still works without the attach/live debugging functionality in the SA (at least in theory, I haven’t taken core debugging for a spin yet).

top: http://cr.openjdk.java.net/~mikael/webrevs/portola/sathreaddb/webrev.00/webrev/
hotspot: http://cr.openjdk.java.net/~mikael/webrevs/portola/sathreaddb/webrev.00/hotspot/webrev/

Cheers,
Mikael