When wasmforge runs as a standalone binary with no source tree on disk,
injectSysshimReplace and injectPuregoSysshimReplace failed with
"cannot find wasmforge module root for sysshim injection" because all
four findModuleRoot() fallback paths returned "".
Three-part fix:
- cmd/gen-build-assets: add addSysshimDir (recursive walk) and include
the internal/sysshim tree under the "sysshim/" prefix in the bundle.
File count rises from ~399 to 442.
- internal/build/asset_cache.go: new file providing
ensureAssetsExtracted(), a process-lifetime sync.Once cache that
extracts build_assets.tar.gz to a temp dir on first call.
- internal/build/compiler.go: add sysshimSourceBase() helper that
prefers the on-disk module root (dev mode) and falls back to the
extracted asset cache (distribution mode); rewire both injection
functions to use it instead of calling findModuleRoot() directly.
michaelweber