kernel-build.mk: add .NOTPARALLEL

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 42876

include/kernel-build.mk

@@ -62,6 +62,8 @@ define BuildKernel
   $(if $(QUILT),$(Build/Quilt))
   $(if $(LINUX_SITE),$(call Download,kernel))
 
+  .NOTPARALLEL:
+
   $(STAMP_PREPARED): $(if $(LINUX_SITE),$(DL_DIR)/$(LINUX_SOURCE))
 	-rm -rf $(KERNEL_BUILD_DIR)
 	-mkdir -p $(KERNEL_BUILD_DIR)