Add LOCAL_EXPORT_C_INCLUDE_DIRS to libunwind and libunwind-ptrace targets

Change-Id: I9c1ddb45c841ee87f43b63087ef092acca4a6fec
diff --git a/Android.mk b/Android.mk
index 321d99b..f3c4e66 100644
--- a/Android.mk
+++ b/Android.mk
@@ -214,6 +214,9 @@
 	-lc \
 	-lpthread \
 
+libunwind_export_c_include_dirs := \
+	$(LOCAL_PATH)/include
+
 ifeq ($(debug),true)
 libunwind_shared_libraries += \
 	liblog \
@@ -261,6 +264,9 @@
 	-lc \
 	-lpthread \
 
+libunwind-ptrace_export_c_include_dirs := \
+	$(LOCAL_PATH)/include
+
 ifeq ($(debug),true)
 libunwind-ptrace_shared_libraries += \
 	liblog \