Build kernel with multi-thread

Author: cradiator

Makefile

@@ -165,7 +165,8 @@ LINUX_MAKE := \
   CROSS_COMPILE=$(TARGET)- \
   LLVM=1 LLVM_IAS=1 \
   V=$(VERBOSE) \
-  O=$(LINUX_OUT)
+  O=$(LINUX_OUT) \
+  -j `nproc`
 
 $(CLANG_DIR):
 	$(warning $(YELLOW)Clang directory $(CLANG_DIR) does not exist, downloading prebuilt binaries $(NC))