Use arm instruction set with clang 7.0 LTO

* surfaceflinger.so uses LTO.
  clang 7.0 LTO inlined more code and some references
  are too far away to use thumb instructions.

Bug: 72619014
Test: run Forrest
Change-Id: Ia09931e93a170ac58007f80da2d580bb9b9635a6
diff --git a/libs/vr/libvrflinger/Android.bp b/libs/vr/libvrflinger/Android.bp
index 23a9853..c762e46 100644
--- a/libs/vr/libvrflinger/Android.bp
+++ b/libs/vr/libvrflinger/Android.bp
@@ -81,6 +81,11 @@
         "-Wno-error=sign-compare", // to fix later
         "-Wno-unused-variable",
     ],
+    arch: {
+        arm: {
+            instruction_set: "arm",
+        },
+    },
     shared_libs: sharedLibraries,
     whole_static_libs: staticLibraries,
     header_libs: headerLibraries,