[source] include: Do not alter KERNELRELEASE for external/git kernels

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/b6746a6ffb738d541b64eb4107e688d36ff86417

commit b6746a6ffb738d541b64eb4107e688d36ff86417
Author: Florian Fainelli <f.fainelli at gmail.com>
AuthorDate: Thu May 11 14:33:42 2017 -0700

    include: Do not alter KERNELRELEASE for external/git kernels
    
    In case we use external and/or git cloned kernels, let the kernel
    determine the appropriate KERNELRELEASE. We cannot used
    LINUX_UNAME_VERSION because that one gets determined at a later time,
    when the kernel is already built proper.
    
    Signed-off-by: Florian Fainelli <f.fainelli at gmail.com>
---
 include/kernel-defaults.mk | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/kernel-defaults.mk b/include/kernel-defaults.mk
index b201865..bca1f1e 100644
--- a/include/kernel-defaults.mk
+++ b/include/kernel-defaults.mk
@@ -24,9 +24,14 @@ KERNEL_MAKEOPTS := -C $(LINUX_DIR) \
 	CONFIG_SHELL="$(BASH)" \
 	$(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='') \
 	$(if $(PKG_BUILD_ID),LDFLAGS_MODULE=--build-id=0x$(PKG_BUILD_ID)) \
-	KERNELRELEASE=$(LINUX_VERSION) \
 	cmd_syscalls=
 
+
+ifeq ($(call qstrip,$(CONFIG_EXTERNAL_KERNEL_TREE))$(call qstrip,$(CONFIG_KERNEL_GIT_CLONE_URI)),)
+  KERNEL_MAKEOPTS += \
+	KERNELRELEASE=$(LINUX_VERSION)
+endif
+
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
   KERNEL_MAKEOPTS += \
 	EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"