Added helper functions to handle concurrent writes to ctx.Stdout/Stderr

Author: cmaglie

Diff for: legacy/builder/container_find_includes.go

@@ -408,7 +408,7 @@ func findIncludesUntilDone(ctx *types.Context, cache *includeCache, sourceFile t
 					return errors.New(tr("Internal error in cache"))
 				}
 			}
-			ctx.Stderr.Write(preproc_stderr)
+			ctx.WriteStderr(preproc_stderr)
 			return errors.WithStack(preproc_err)
 		}
 

Diff for: legacy/builder/types/context.go

@@ -252,3 +252,21 @@ func (ctx *Context) Warn(msg string) {
 	}
 	ctx.stdLock.Unlock()
 }
+
+func (ctx *Context) WriteStdout(data []byte) (int, error) {
+	ctx.stdLock.Lock()
+	defer ctx.stdLock.Unlock()
+	if ctx.Stdout == nil {
+		return os.Stdout.Write(data)
+	}
+	return ctx.Stdout.Write(data)
+}
+
+func (ctx *Context) WriteStderr(data []byte) (int, error) {
+	ctx.stdLock.Lock()
+	defer ctx.stdLock.Unlock()
+	if ctx.Stderr == nil {
+		return os.Stderr.Write(data)
+	}
+	return ctx.Stderr.Write(data)
+}