recovery: Switch to clang

And a few trival fixes to suppress warnings.

Change-Id: Id28e3581aaca4bda59826afa80c0c1cdfb0442fc
(cherry picked from commit 80e46e08de5f65702fa7f7cd3ef83f905d919bbc)
diff --git a/minzip/Android.mk b/minzip/Android.mk
index 045f355..48d26bc 100644
--- a/minzip/Android.mk
+++ b/minzip/Android.mk
@@ -16,6 +16,8 @@
 
 LOCAL_MODULE := libminzip
 
+LOCAL_CLANG := true
+
 LOCAL_CFLAGS += -Wall
 
 include $(BUILD_STATIC_LIBRARY)
diff --git a/minzip/Zip.c b/minzip/Zip.c
index 40712e0..a64c833 100644
--- a/minzip/Zip.c
+++ b/minzip/Zip.c
@@ -506,7 +506,6 @@
     void *cookie)
 {
     long result = -1;
-    unsigned char readBuf[32 * 1024];
     unsigned char procBuf[32 * 1024];
     z_stream zstream;
     int zerr;
@@ -603,7 +602,6 @@
     void *cookie)
 {
     bool ret = false;
-    off_t oldOff;
 
     switch (pEntry->compression) {
     case STORED: