recovery: Switch to clang

And a few trival fixes to suppress warnings.

Change-Id: Id28e3581aaca4bda59826afa80c0c1cdfb0442fc
(cherry picked from commit 80e46e08de5f65702fa7f7cd3ef83f905d919bbc)
diff --git a/applypatch/Android.mk b/applypatch/Android.mk
index 4984093..4936db2 100644
--- a/applypatch/Android.mk
+++ b/applypatch/Android.mk
@@ -13,8 +13,10 @@
 # limitations under the License.
 
 LOCAL_PATH := $(call my-dir)
+
 include $(CLEAR_VARS)
 
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := applypatch.c bspatch.c freecache.c imgpatch.c utils.c
 LOCAL_MODULE := libapplypatch
 LOCAL_MODULE_TAGS := eng
@@ -25,6 +27,7 @@
 
 include $(CLEAR_VARS)
 
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := main.c
 LOCAL_MODULE := applypatch
 LOCAL_C_INCLUDES += bootable/recovery
@@ -35,6 +38,7 @@
 
 include $(CLEAR_VARS)
 
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := main.c
 LOCAL_MODULE := applypatch_static
 LOCAL_FORCE_STATIC_EXECUTABLE := true
@@ -47,6 +51,7 @@
 
 include $(CLEAR_VARS)
 
+LOCAL_CLANG := true
 LOCAL_SRC_FILES := imgdiff.c utils.c bsdiff.c
 LOCAL_MODULE := imgdiff
 LOCAL_FORCE_STATIC_EXECUTABLE := true