shiroikuma-gcfs

Cross-compile the gcfs Termux/arm64 binary via build-termux.sh, then auto-deliver it — run `adb devices` UNSANDBOXED and, if a device is present, `adb push` it to /sdcard/tmp without asking. Use whenever 白い熊 asks to build gcfs, build the binary, make a Termux build, or build and send to the phone.

Merge new upstream commits from hardcore-sushi/libgocryptfs into our custom branch. Use when 白い熊 says upstream libgocryptfs has changes, asks to sync/update to upstream, or to rebase custom onto upstream.