Better seccomp/kuser_helper diagnostics from debuggerd.

Also switch to Android.bp for crasher.

Bug: http://b/34629282 (seccomp)
Bug: http://b/34705831 (seccomp)
Bug: http://b/34884086 (kuser_helpers)
Test: manual
Change-Id: I8ee79c635518faeba751742919af69a505b5e3e1
diff --git a/debuggerd/Android.bp b/debuggerd/Android.bp
index 6dc6675..ca881aa 100644
--- a/debuggerd/Android.bp
+++ b/debuggerd/Android.bp
@@ -195,3 +195,7 @@
 
     init_rc: ["tombstoned/tombstoned.rc"]
 }
+
+subdirs = [
+    "crasher",
+]