Print ABI in backtraces.

This lets the stack tool figure out which toolchain to use
automatically.

Change-Id: Ia235d6904622423fe6fbc7b0315a1861e52a41ad
diff --git a/debuggerd/backtrace.cpp b/debuggerd/backtrace.cpp
index 50bc167..c4a2143 100644
--- a/debuggerd/backtrace.cpp
+++ b/debuggerd/backtrace.cpp
@@ -49,8 +49,9 @@
   struct tm tm;
   localtime_r(&t, &tm);
   char timestr[64];
+  _LOG(log, logtype::BACKTRACE, "\n\nABI: '%s'\n", ABI_STRING);
   strftime(timestr, sizeof(timestr), "%F %T", &tm);
-  _LOG(log, logtype::BACKTRACE, "\n\n----- pid %d at %s -----\n", pid, timestr);
+  _LOG(log, logtype::BACKTRACE, "\n----- pid %d at %s -----\n", pid, timestr);
 
   if (procname) {
     _LOG(log, logtype::BACKTRACE, "Cmd line: %s\n", procname);