recovery: Switch to clang

And a few trival fixes to suppress warnings.

Change-Id: I38734b5f4434643e85feab25f4807b46a45d8d65
diff --git a/minui/Android.mk b/minui/Android.mk
index 52f0662..5584612 100644
--- a/minui/Android.mk
+++ b/minui/Android.mk
@@ -39,6 +39,7 @@
 
 # Used by OEMs for factory test images.
 include $(CLEAR_VARS)
+LOCAL_CLANG := true
 LOCAL_MODULE := libminui
 LOCAL_WHOLE_STATIC_LIBRARIES += libminui
 LOCAL_SHARED_LIBRARIES := libpng