Don't enable ADB authentication on eng builds

Change-Id: Ibc618e1644080984eb9a409178a2d2bcd76ddf77
diff --git a/common.mk b/common.mk
index b749c01..8b1ffb3 100644
--- a/common.mk
+++ b/common.mk
@@ -117,8 +117,10 @@
 FAOSP_VERSION := $(TARGET_DEVICE)-$(shell date -u +%Y%m%d)
 PRODUCT_PROPERTY_OVERRIDES += ro.faosp.version=$(FAOSP_VERSION)
 
+ifneq ($(TARGET_BUILD_VARIANT),eng)
 # Enable ADB authentication
 ADDITIONAL_DEFAULT_PROPERTIES += ro.adb.secure=1
+endif
 
 # Chromium Prebuilt
 ifeq ($(PRODUCT_PREBUILT_WEBVIEWCHROMIUM),yes)