Add a project wide clang switch.

I'll probably make this the default soon, but I'm not brave enough to
do that without checking the recovery image first.

Change-Id: I9cde687b08a588e3797645a308f381e4ec553447
diff --git a/adb/Android.mk b/adb/Android.mk
index 327591f..da5015a 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -5,6 +5,8 @@
 
 LOCAL_PATH:= $(call my-dir)
 
+ADB_CLANG :=
+
 # libadb
 # =========================================================
 
@@ -33,6 +35,7 @@
 LIBADB_windows_SRC_FILES := get_my_path_windows.c sysdeps_win32.c usb_windows.c
 
 include $(CLEAR_VARS)
+LOCAL_CLANG := $(ADB_CLANG)
 LOCAL_MODULE := libadbd
 LOCAL_CFLAGS := $(LIBADB_CFLAGS) -DADB_HOST=0
 LOCAL_SRC_FILES := \
@@ -46,6 +49,7 @@
 include $(BUILD_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)
+LOCAL_CLANG := $(ADB_CLANG)
 LOCAL_MODULE := libadb
 LOCAL_CFLAGS := $(LIBADB_CFLAGS) -DADB_HOST=1
 LOCAL_SRC_FILES := \
@@ -86,6 +90,8 @@
   endif
 endif
 
+LOCAL_CLANG := $(ADB_CLANG)
+
 LOCAL_SRC_FILES := \
 	adb_main.c \
 	console.c \
@@ -130,6 +136,8 @@
 
 include $(CLEAR_VARS)
 
+LOCAL_CLANG := $(ADB_CLANG)
+
 LOCAL_SRC_FILES := \
 	adb_main.c \
 	services.c \