Use -Werror in frameworks/native/libs/vr

* Suppress/fix warnings of unused variable, parameter,
  private-field, and function.
* Fix warnings about typedef missing declarator.
* Use -Wno-error to keep existing warnings, to fix later.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: Ifb82fcd76fcb5d9c9d9f017f2541581661493bd5
diff --git a/libs/vr/libvrsensor/Android.bp b/libs/vr/libvrsensor/Android.bp
index abad78b..1a15b6a 100644
--- a/libs/vr/libvrsensor/Android.bp
+++ b/libs/vr/libvrsensor/Android.bp
@@ -40,6 +40,10 @@
 
 cc_library {
     srcs: sourceFiles,
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
     export_include_dirs: includeFiles,
     static_libs: staticLibraries,
     shared_libs: sharedLibraries,