mod+tools+Makefile:separate tools different module

Separated the tools to different go module to avoid having tools
dependencies on the main module.

tools/tools.go

@@ -0,0 +1,18 @@
+//go:build tools
+// +build tools
+
+package lnd
+
+// The other imports represent our build tools. Instead of defining a commit we
+// want to use for those golang based tools, we use the go mod versioning system
+// to unify the way we manage dependencies. So we define our build tool
+// dependencies here and pin the version in go.mod.
+import (
+	_ "github.com/btcsuite/btcd"
+	_ "github.com/dvyukov/go-fuzz/go-fuzz"
+	_ "github.com/dvyukov/go-fuzz/go-fuzz-build"
+	_ "github.com/dvyukov/go-fuzz/go-fuzz-dep"
+	_ "github.com/golangci/golangci-lint/cmd/golangci-lint"
+	_ "github.com/ory/go-acc"
+	_ "github.com/rinchsan/gosimports/cmd/gosimports"
+)