Fix build from implicit declaration.

Turn the warning on by default and turn on -Werror so this doesn't
happen next time.

Change-Id: Id65bf0cb63bbf0ff224655b425463ae2f55435df
diff --git a/minadbd/Android.mk b/minadbd/Android.mk
index f4b060b..dce004f 100644
--- a/minadbd/Android.mk
+++ b/minadbd/Android.mk
@@ -1,22 +1,22 @@
 # Copyright 2005 The Android Open Source Project
-#
-# Android.mk for adb
-#
 
 LOCAL_PATH:= $(call my-dir)
 
-# minadbd library
-# =========================================================
-
 include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := \
-	adb_main.c \
-	fuse_adb_provider.c \
-	services.c \
+    adb_main.c \
+    fuse_adb_provider.c \
+    services.c \
 
-LOCAL_CFLAGS := -O2 -g -DADB_HOST=0 -Wall -Wno-unused-parameter
-LOCAL_CFLAGS += -D_XOPEN_SOURCE -D_GNU_SOURCE
+LOCAL_CFLAGS := \
+    -Wall -Werror \
+    -Wno-unused-parameter \
+    -Wimplicit-function-declaration \
+    -D_GNU_SOURCE \
+    -D_XOPEN_SOURCE \
+    -DADB_HOST=0 \
+
 LOCAL_C_INCLUDES := bootable/recovery system/core/adb
 LOCAL_WHOLE_STATIC_LIBRARIES := libadbd