package/linux: trash stderr in LINUX_VERSION_PROBED

The Linux buildsystem tries to run the compiler even just for
'kernelrelease' (which we store in LINUX_VERSION_PROBED) and we
sometimes need to use it before the toolchain is available; thus
we get spurious errors on stderr.

Consign stderr to oblivion when computing the 'kernelrelease'.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
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 = `$(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 2>/dev/null`
 
 ifeq ($(BR2_LINUX_KERNEL_USE_INTREE_DTS),y)
 KERNEL_DTS_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_INTREE_DTS_NAME))