Reduce HTTP requests for checksum file in fetch-checksum

[eleanorLYJ]

After adding more test cases, the CI pipeline fails due to excessive HTTP requests to GitHub during the fetch-checksum step. This triggers rate-limiting errors (403: rate limit exceeded).

Proposed Solution:

Check if the checksum file exists and is less than one day old before fetching it. This will reduce unnecessary requests while ensuring the file is up-to-date.

[jserv]

Network quality issues may sometimes cause unexpected disconnections when downloading from certain remote sites, requiring retries.

[vacantron]

It seems to be too many requests in a short period that make artifact is called when running make all . Maybe maintain the local copies of sha1sum files which use the recently commit hash as the postfix of them to reduce the refetching?

[vacantron]

I think the main reason causing this is

rv32emu/mk/artifact.mk

Lines 39 to 47 in c9dfd36

	ifeq ($(call has, PREBUILT), 1)
	ifeq ($(call has, SYSTEM), 1)
	LATEST_RELEASE := $(shell wget -q https://api.github.com/repos/sysprog21/rv32emu-prebuilt/releases -O- | grep '"tag_name"' | grep "Linux-Image" | head -n 1 | sed -E 's/.*"tag_name": "([^"]+)".*/\1/')
	else ifeq ($(call has, ARCH_TEST), 1)
	LATEST_RELEASE := $(shell wget -q https://api.github.com/repos/sysprog21/rv32emu-prebuilt/releases -O- | grep '"tag_name"' | grep "sail" | head -n 1 | sed -E 's/.*"tag_name": "([^"]+)".*/\1/')
	else
	LATEST_RELEASE := $(shell wget -q https://api.github.com/repos/sysprog21/rv32emu-prebuilt/releases -O- | grep '"tag_name"' | grep "ELF" | head -n 1 | sed -E 's/.*"tag_name": "([^"]+)".*/\1/')
	endif
	PREBUILT_BLOB_URL = https://github.com/sysprog21/rv32emu-prebuilt/releases/download/$(LATEST_RELEASE)

Every time we run make, the GitHub API is called. We can reduce the number of HTTP requests by checking the prebuilt files is existing or not.

However, in CI, we always run make distclean before building. The method mentioned above would not work.

rv32emu/Makefile

Lines 418 to 421 in c9dfd36

	distclean: clean
	-$(RM) $(DOOM_DATA) $(QUAKE_DATA) $(BUILDROOT_DATA) $(LINUX_DATA)
	$(RM) -r $(OUT)/linux-image
	$(RM) -r $(TIMIDITY_DATA)