Add vendor to improve building speed.

This also adds ability to be built in network-constrained environment.

vendor/github.com/cloudwego/base64x/Makefile

@@ -0,0 +1,29 @@
+.PHONY: all clean
+
+CFLAGS := -mavx
+CFLAGS += -mavx2
+CFLAGS += -mno-bmi
+CFLAGS += -mno-red-zone
+CFLAGS += -fno-asynchronous-unwind-tables
+CFLAGS += -fno-stack-protector
+CFLAGS += -fno-exceptions
+CFLAGS += -fno-builtin
+CFLAGS += -fno-rtti
+CFLAGS += -nostdlib
+CFLAGS += -O3
+
+NATIVE_ASM := $(wildcard native/*.S)
+NATIVE_SRC := $(wildcard native/*.h)
+NATIVE_SRC += $(wildcard native/*.c)
+
+all: native_amd64.s
+
+clean:
+	rm -vf native_text_amd64.go native_subr_amd64.go output/*.s
+
+native_amd64.s: ${NATIVE_SRC} ${NATIVE_ASM} native_amd64.go
+	mkdir -p output
+	clang ${CFLAGS} -S -o output/native.s native/native.c
+	python3 tools/asm2asm/asm2asm.py -r native_amd64.go output/native.s ${NATIVE_ASM}
+	awk '{gsub(/Text__native_entry__/, "text__native_entry__")}1' native_text_amd64.go > native_text_amd64.go.tmp && mv native_text_amd64.go.tmp native_text_amd64.go
+	awk '{gsub(/Funcs/, "funcs")}1' native_subr_amd64.go > native_subr_amd64.go.tmp && mv native_subr_amd64.go.tmp native_subr_amd64.go