Capture backtraces during build_test

We're seeing random ckati segfaults, and ASAN only hides the problem, so
attempt to capture more information.

Bug: 36182021
Test: build/soong/build_test.bash, kill -SIGSEGV <ckati>
Change-Id: I854ae846df0c47f69ec8d39b9a3d9e6f482e0854
diff --git a/build_test.bash b/build_test.bash
index f833366..ab841cb 100755
--- a/build_test.bash
+++ b/build_test.bash
@@ -30,5 +30,11 @@
 export TOP=$(cd $(dirname ${BASH_SOURCE[0]})/../..; PWD= /bin/pwd)
 source "${TOP}/build/soong/cmd/microfactory/microfactory.bash"
 
+case $(uname) in
+  Linux)
+    export LD_PRELOAD=/lib/x86_64-linux-gnu/libSegFault.so
+    ;;
+esac
+
 build_go multiproduct_kati android/soong/cmd/multiproduct_kati
 exec "$(getoutdir)/multiproduct_kati" "$@"