TWRP device version string

For building through jenkins. Export a variable to the shell
so that we don't monkey patch variables.h and keep the git tag
clean in the version string.
Jenkins will export the variable TW_DEVICE_VERSION=n where n > 0.
The makefile will use this variable to show the device string
in twrp startup. For mass production builds, omit the
environment variable to default to 0.

Change-Id: I0d6eb764255d7069c0fb4a378522a009cfe4054f
diff --git a/Android.mk b/Android.mk
index d456bfc..80d7081 100644
--- a/Android.mk
+++ b/Android.mk
@@ -40,6 +40,12 @@
 
 TARGET_RECOVERY_GUI := true
 
+ifneq ($(TW_DEVICE_VERSION),)
+    LOCAL_CFLAGS += -DTW_DEVICE_VERSION='"-$(TW_DEVICE_VERSION)"'
+else
+    LOCAL_CFLAGS += -DTW_DEVICE_VERSION='"-0"'
+endif
+
 LOCAL_SRC_FILES := \
     twrp.cpp \
     fixContexts.cpp \
@@ -164,7 +170,7 @@
 ifeq ($(TWHAVE_SELINUX), true)
     LOCAL_C_INCLUDES += external/libselinux/include
     LOCAL_SHARED_LIBRARIES += libselinux
-    LOCAL_CFLAGS += -DHAVE_SELINUX -g
+    LOCAL_CFLAGS += -DHAVE_SELINUX
     ifneq ($(TARGET_USERIMAGES_USE_EXT4), true)
         LOCAL_CFLAGS += -DUSE_EXT4
         LOCAL_C_INCLUDES += system/extras/ext4_utils