ART: Factor out gAborting

Cut dependencies on base/logging.h by moving gAborting to its
own header. Leave the static storage in logging.cc.

Test: m
Change-Id: Ib2ca880e15f9cb50cb9aab803784826bb46efb5e
diff --git a/runtime/signal_catcher.cc b/runtime/signal_catcher.cc
index bf5d718..d9c4da9 100644
--- a/runtime/signal_catcher.cc
+++ b/runtime/signal_catcher.cc
@@ -35,6 +35,7 @@
 
 #include "arch/instruction_set.h"
 #include "base/file_utils.h"
+#include "base/logging.h"  // For GetCmdLine.
 #include "base/time_utils.h"
 #include "base/unix_file/fd_file.h"
 #include "class_linker.h"