Fix mips/mips64/x86_64 host builds.

We don't want to use GCC for the host.

Change-Id: I05523a004d14dfaf0a2cab33fe5b10cee6a797e8
diff --git a/Android.build.mk b/Android.build.mk
index f7b6fe1..5d91049 100644
--- a/Android.build.mk
+++ b/Android.build.mk
@@ -24,8 +24,9 @@
 LOCAL_MODULE := $(libunwind_module)
 LOCAL_MODULE_TAGS := $(libunwind_module_tag)
 ifeq ($(libunwind_build_type),host)
-# Always make host multilib
+# Always make host multilib, and always use clang.
 LOCAL_MULTILIB := both
+LOCAL_CLANG := true
 else
 LOCAL_MULTILIB := $($(libunwind_module)_multilib)
 endif