perf: add more compiler flags

I don't think these have any positive effect, but they tell the compiler
to make code for the current architecture and make use of optimizations
that are specific to that architecture.

lua/wincent/commandt/lib/Makefile

@@ -3,7 +3,7 @@
 
 SHELL := /bin/bash
 
-CCFLAGS ?= -std=gnu17 -Wall -Wextra -Wno-unused-parameter
+CCFLAGS ?= -std=gnu17 -march=native -mtune=native -Wall -Wextra -Wno-unused-parameter
 
 # Allow augmentation from the command-line with CFLAGS:
 CCFLAGS += $(CFLAGS)