Fix libbacktrace host build.

On host build, libbacktrace relies on libcutils to provide gettid()
function.

Change-Id: Iad83384ea699ca024b71b73cef26755287c9e6fe
diff --git a/libbacktrace/Android.mk b/libbacktrace/Android.mk
index 9c6742e..5d3dd86 100644
--- a/libbacktrace/Android.mk
+++ b/libbacktrace/Android.mk
@@ -68,6 +68,7 @@
 # Use static llvm libraries on host to remove dependency on 32-bit llvm shared library
 # which is not included in the prebuilt.
 libbacktrace_static_libraries_host := \
+	libcutils \
 	libLLVMObject \
 	libLLVMBitReader \
 	libLLVMMC \
diff --git a/libbacktrace/Backtrace.cpp b/libbacktrace/Backtrace.cpp
index df94280..3c8f879 100644
--- a/libbacktrace/Backtrace.cpp
+++ b/libbacktrace/Backtrace.cpp
@@ -27,8 +27,6 @@
 #include <backtrace/Backtrace.h>
 #include <backtrace/BacktraceMap.h>
 
-#include <cutils/threads.h>
-
 #include "BacktraceLog.h"
 #include "BacktraceOffline.h"
 #include "thread_utils.h"
diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
index d339550..8e22366 100644
--- a/libbacktrace/BacktraceCurrent.cpp
+++ b/libbacktrace/BacktraceCurrent.cpp
@@ -29,8 +29,6 @@
 #include <backtrace/Backtrace.h>
 #include <backtrace/BacktraceMap.h>
 
-#include <cutils/threads.h>
-
 #include "BacktraceCurrent.h"
 #include "BacktraceLog.h"
 #include "ThreadEntry.h"
diff --git a/libbacktrace/thread_utils.h b/libbacktrace/thread_utils.h
index df83581..9590657 100644
--- a/libbacktrace/thread_utils.h
+++ b/libbacktrace/thread_utils.h
@@ -19,6 +19,10 @@
 
 #include <unistd.h>
 
+#if !defined(__ANDROID__)
+#include <cutils/threads.h>
+#endif
+
 __BEGIN_DECLS
 
 int tgkill(int tgid, int tid, int sig);