recovery: Switch to clang

And a few trival fixes to suppress warnings.

Change-Id: I38734b5f4434643e85feab25f4807b46a45d8d65
diff --git a/mtdutils/Android.mk b/mtdutils/Android.mk
index f04355b..b7d35c2 100644
--- a/mtdutils/Android.mk
+++ b/mtdutils/Android.mk
@@ -6,10 +6,12 @@
 	mounts.c
 
 LOCAL_MODULE := libmtdutils
+LOCAL_CLANG := true
 
 include $(BUILD_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := flash_image.c
 LOCAL_MODULE := flash_image
 LOCAL_MODULE_TAGS := eng