docs: add verified build instructions; fix bincmp ssdeep API

- README "Building From Source" section covering all Go and Rust tools;
  every command tested (rustc, go build, goipgrep make build/test)
- bincmp: ssdeep.HashFromFile does not exist in pinned ssdeep v0.4.0,
  switch to FuzzyFilename; fix two go vet warnings
- ignore in-place build outputs for bincmp/gopname/goinfo

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -15,5 +15,8 @@ bin/
 .ruff_cache/
 
 # compiled binaries that live next to their source
+projects/go-tools/bincmp/bincmp
+projects/go-tools/gopname/gopname
+projects/go-tools/goinfo/goinfo
 projects/go-tools/gosoft/gosoft
 archive/experimental/go/tarsum/tarsum