run make jobs by cpu count

Makefile

@@ -168,7 +168,7 @@ define build_proj_tmpl
 PROS += $$(basename $$(value $(1)_PRO)).build
 $(1)_MAKE := $$(basename $$(value $(1)_PRO)).build/Makefile
 $$(value $(1)): $$(value $(1)_MAKE)
-	cd $$(dir $$(value $(1)_MAKE)) && make -j
+	cd $$(dir $$(value $(1)_MAKE)) && make -j $$(grep processor /proc/cpuinfo | wc -l)
 endef
 
 .PHONY : all bin lib clean