Never enable LTO for libunwind_llvm

Bug: http://b/78476183

Symbols from libunwind_llvm are supposed to have hidden visibility and
enforced with '-Wl,--exclude-libs'.  With LTO, the archive with these
symbols may not match the file to --exclude-libs, thereby causing them
to be exported.

Test: Verify that libhwbinder.so with LTO has hidden visiblity for
_Unwind_VRS_Set

Change-Id: I84292e97d6af42448165f515f2e11c6bc2ee9f63
diff --git a/Android.bp b/Android.bp
index 75c72f8..c71d35f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -65,4 +65,7 @@
             enabled: true,
         },
     },
+    lto: {
+        never: true,
+    }
 }