Remove trailing newlines from abort message.

The tombstone will add a newline after the abort message, so remove
any trailing newlines before saving/printing.

Bug: 196414062

Test: Unit tests pass.
Test: Set system property debug.debuggerd.translate_proto_to_text to 0
test: and unit tests still pass.
Change-Id: I0d3dc215eb5d8be93d99e5b9d4f0a14b1d61396d
diff --git a/debuggerd/libdebuggerd/tombstone.cpp b/debuggerd/libdebuggerd/tombstone.cpp
index 9c01f15..ff03bcd 100644
--- a/debuggerd/libdebuggerd/tombstone.cpp
+++ b/debuggerd/libdebuggerd/tombstone.cpp
@@ -232,6 +232,12 @@
     return;
   }
 
+  // Remove any trailing newlines.
+  size_t index = length;
+  while (index > 0 && (msg[index - 1] == '\0' || msg[index - 1] == '\n')) {
+    --index;
+  }
+  msg[index] = '\0';
   _LOG(log, logtype::HEADER, "Abort message: '%s'\n", &msg[0]);
 }