image build: CLI fails with CGO-less build (SQLite layer-cache stub) even with --no-cache

Summary

nanofuse image build cannot run when the nanofuse CLI is built with CGO_ENABLED=0 (the default mage cli build), because it opens a SQLite layer-cache database at startup:

Error: cannot create layer cache: failed to open cache database: failed to enable foreign keys:
Binary was compiled with 'CGO_ENABLED=0', go-sqlite3 requires cgo to work. This is a stub

--no-cache does not avoid this — the cache DB is still initialized:

No-cache:  true
Error: cannot create layer cache: ... go-sqlite3 requires cgo to work. This is a stub

Details

• The daemon (nanofused) is built with CGO (mage notes "with CGO for SQLite"), but the CLI (nanofuse) is not — yet the CLI hosts image build, which needs SQLite for the layer cache.
• Workaround: rebuild the CLI with CGO_ENABLED=1 go build ./cmd/nanofuse (then image build proceeds past this point).

Fix direction

Either build the nanofuse CLI with CGO in the mage cli target (since image build needs it), or make --no-cache genuinely skip opening the cache DB (no SQLite dependency when caching is off), or move the layer cache to a CGO-free store.

Impact

image build is unusable from a standard CLI build; only a manually CGO-rebuilt CLI works.

Start with the mage cli target and the nanofuse image build startup path, focusing on where the SQLite layer cache is initialized and how --no-cache is handled. Determine which fix direction fits the project, then verify that a standard CGO-less CLI can run image build and that no-cache behavior avoids an unnecessary cache database dependency.