linux: use backtick instead of $(shell ...) make function

Verified that LINUX_VERSION_PROBED is only used in "-quoted commands
(actually, usually it's not quoted).

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

linux/linux.mk

@@ -76,7 +76,7 @@ LINUX_MAKE_ENV = \
 
 # Get the real Linux version, which tells us where kernel modules are
 # going to be installed in the target filesystem.
-LINUX_VERSION_PROBED = $(shell $(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) --no-print-directory -s kernelrelease)
+LINUX_VERSION_PROBED = `$(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) --no-print-directory -s kernelrelease`
 
 ifeq ($(BR2_LINUX_KERNEL_USE_INTREE_DTS),y)
 KERNEL_DTS_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_INTREE_DTS_NAME))