sdm: Save debug logs on pingpong timeout

Save xlogs in /data/vendor/display on pingpong timeout for
userdebug/eng builds

Change-Id: I8a60452af44797c8a425e84706375d3209612692
diff --git a/common.mk b/common.mk
index 88d1aee..66f0a11 100644
--- a/common.mk
+++ b/common.mk
@@ -35,6 +35,10 @@
     common_flags += -DUSE_GRALLOC1
 endif
 
+ifneq (,$(filter userdebug eng, $(TARGET_BUILD_VARIANT)))
+    common_flags += -DUSER_DEBUG
+endif
+
 common_includes := system/core/base/include
 CHECK_VERSION_LE = $(shell if [ $(1) -le $(2) ] ; then echo true ; else echo false ; fi)
 PLATFORM_SDK_NOUGAT = 25