Enable libunwind for mips.

Change-Id: Ib1d7bea0cb7ac09a9e15c7f429ecfd944649fc87
diff --git a/libbacktrace/Android.mk b/libbacktrace/Android.mk
index 33af0a3..2e56756 100755
--- a/libbacktrace/Android.mk
+++ b/libbacktrace/Android.mk
@@ -47,7 +47,7 @@
 	libgccdemangle \
 
 # To enable using libunwind on each arch, add it to this list.
-libunwind_architectures := arm arm64 x86 x86_64
+libunwind_architectures := arm arm64 mips x86 x86_64
 
 ifeq ($(TARGET_ARCH),$(filter $(TARGET_ARCH),$(libunwind_architectures)))
 libbacktrace_src_files += \