Allow the use of GDB/LLDB for debugging

If the environment variable USE_GDB exists this plugin will pause
before the EUNIT tests so that you can attach a debugger to the VM.

plugins/rebar_gdb_plugin.erl

@@ -0,0 +1,13 @@
+-module(rebar_gdb_plugin).
+-compile(export_all).
+
+pre_eunit(_Config, _AppFile) ->
+    case os:getenv("USE_GDB") of
+        false ->
+            ok;
+        _ ->
+            Prompt = io_lib:format("GDB Attach to: ~s~n", [os:getpid()]),
+            io:get_line(Prompt)
+    end,
+    ok.
+

rebar.config

@@ -32,3 +32,8 @@
         eunit_surefire, [{dir,"."}]
     }}
 ]}.
+
+{plugins, [
+    rebar_gdb_plugin
+]}.
+