kvdb: exclude anything bbolt related from JS builds

Since bbolt uses syscalls for memory mapping that aren't available in
JS/WASM builds, we need to make sure we don't reference that code at
all. Otherwise we can't use parts of lnd as a library in projects that
are being compiled down to a WASM binary.

kvdb/backend.go

@@ -1,3 +1,5 @@
+// +build !js
+
 package kvdb
 
 import (

kvdb/backend_js.go

@@ -0,0 +1,48 @@
+package kvdb
+
+import (
+	"fmt"
+	"time"
+)
+
+// BoltBackendConfig is a struct that holds settings specific to the bolt
+// database backend.
+type BoltBackendConfig struct {
+	// DBPath is the directory path in which the database file should be
+	// stored.
+	DBPath string
+
+	// DBFileName is the name of the database file.
+	DBFileName string
+
+	// NoFreelistSync, if true, prevents the database from syncing its
+	// freelist to disk, resulting in improved performance at the expense of
+	// increased startup time.
+	NoFreelistSync bool
+
+	// AutoCompact specifies if a Bolt based database backend should be
+	// automatically compacted on startup (if the minimum age of the
+	// database file is reached). This will require additional disk space
+	// for the compacted copy of the database but will result in an overall
+	// lower database size after the compaction.
+	AutoCompact bool
+
+	// AutoCompactMinAge specifies the minimum time that must have passed
+	// since a bolt database file was last compacted for the compaction to
+	// be considered again.
+	AutoCompactMinAge time.Duration
+
+	// DBTimeout specifies the timeout value to use when opening the wallet
+	// database.
+	DBTimeout time.Duration
+}
+
+// GetBoltBackend opens (or creates if doesn't exits) a bbolt backed database
+// and returns a kvdb.Backend wrapping it.
+func GetBoltBackend(cfg *BoltBackendConfig) (Backend, error) {
+	return nil, fmt.Errorf("bolt backend not supported in WebAssembly")
+}
+
+func GetTestBackend(path, name string) (Backend, func(), error) {
+	return nil, nil, fmt.Errorf("bolt backend not supported in WebAssembly")
+}

kvdb/bolt_compact.go

@@ -2,6 +2,8 @@
 // implemented in this file:
 // https://github.com/etcd-io/bbolt/blob/master/cmd/bbolt/main.go
 
+// +build !js
+
 package kvdb
 
 import (