Fix mips build.

Don't build for mips, none of this is supported on mips.

Bug: 23762183

Test: Mips build passes.
Change-Id: Iba89466a7bc13856f8fcd59ca0708a30f417b6c6
diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index 27221af..a5af0a0 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -31,6 +31,15 @@
         },
     },
 
+    arch: {
+        mips: {
+            enabled: false,
+        },
+        mips64: {
+            enabled: false,
+        },
+    },
+
     multilib: {
         lib32: {
             suffix: "32",