https-dns-proxy: update to 2026.03.18-4

[stangri]

Maintainer: me
Compile tested: x86_64, Dell EMC Edge620, OpenWrt 25.12.1
Run tested: x86_64, Dell EMC Edge620, OpenWrt 25.12.1

Description:
Robustify nftables notrack generation

Makefile:

• Bump PKG_RELEASE to 4.
• Add install rule to create /usr/share/nftables.d/ruleset-post.

files/etc/init.d/https-dns-proxy:

• Check if 'nft' command exists before generating rules.
• Add robust error handling for directory creation and file writing.
• Log errors when directory creation or file writing fails.

tests/run_tests.sh:

• Add test case for 'nft' binary absence, confirming no-op behavior.
• Add test case for mkdir failure during notrack rule generation

[stangri]

@aparcar @hnyman @BKPepe -- I've had reports that despite mkdir in the init script in release 3, this directory was still missing. As far as I understand there are no side effects from having this in the Makefile, but I'd still like a feedback on this.

[BKPepe]

What I think is happening here (I haven't gone through all your changes yet) is that the folder is empty, which is why it gets removed and is still missing. There should be at least something in there. :) What most people do in this case is create an empty file to prevent the empty folder from being removed. For example, search for touch (like it's done in syslog-ng, netdata, etc.).

[stangri]

@BKPepe thanks for your prompt reply, so your recommendation before resorting to having a folder in the Makefile, I should try touching a file in there immediately after mkdir -p?