Don't allow adb to run as root in user builds.

Change-Id: I4fbd7beb7f76c68fead1a89b745f0dfb931b4597

adb/Android.mk

@@ -133,6 +133,10 @@ ifeq ($(TARGET_ARCH),arm)
 LOCAL_CFLAGS += -DANDROID_GADGET=1
 endif
 
+ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
+LOCAL_CFLAGS += -DALLOW_ADBD_ROOT=1
+endif
+
 LOCAL_MODULE := adbd
 
 LOCAL_FORCE_STATIC_EXECUTABLE := true

adb/adb.c

@@ -844,6 +844,9 @@ void build_local_name(char* target_str, size_t target_size, int server_port)
 
 #if !ADB_HOST
 static int should_drop_privileges() {
+#ifndef ALLOW_ADBD_ROOT
+    return 1;
+#else /* ALLOW_ADBD_ROOT */
     int secure = 0;
     char value[PROPERTY_VALUE_MAX];
 
@@ -869,6 +872,7 @@ static int should_drop_privileges() {
         }
     }
     return secure;
+#endif /* ALLOW_ADBD_ROOT */
 }
 #endif /* !ADB_HOST */