build/log: add log types + NewSubLogger

build/log_default.go

@@ -0,0 +1,18 @@
+// +build !stdlog,!nolog
+
+package build
+
+import "os"
+
+// LoggingType is a log type that writes to both stdout and the log rotator, if
+// present.
+const LoggingType = LogTypeDefault
+
+// Write writes the byte slice to both stdout and the log rotator, if present.
+func (w *LogWriter) Write(b []byte) (int, error) {
+	os.Stdout.Write(b)
+	if w.RotatorPipe != nil {
+		w.RotatorPipe.Write(b)
+	}
+	return len(b), nil
+}