kernel: unify version

kernel/Makefile

@@ -12,6 +12,12 @@ obj-y += embed_ksud.o
 obj-y += kernel_compat.o
 
 obj-y += selinux/
+# We must use the absolute path to git, otherwise the build will fail if git is not in the PATH
+KSU_GIT_VERSION := $(shell cd $(srctree)/$(src);/usr/bin/git rev-list --count HEAD)
+ifeq ($(KSU_GIT_VERSION),)
+$(error Get git version failed, please make sure git is installed in /usr/bin/git)
+endif
+ccflags-y += -DKSU_GIT_VERSION=$(KSU_GIT_VERSION)
 
 ifndef EXPECTED_SIZE
 EXPECTED_SIZE := 0x033b