为什么只有在指定文件名的情况下，用ldflag -X生成的build才起作用？

Question

I have the file playground.go:

package main

import (
  "fmt"
)

var GitCommit string

func main() {
  fmt.Printf("Hello world, version: %s
", GitCommit)
}

why the behavior of the build ldflag -X depends on specifying the source filename?:

# CASE 1
$ go build -ldflags "-X main.GitCommit=abc" && ./go_playground
Hello world, version: 

$ go tool nm go_playground
52a900 D main.GitCommit

# CASE 2
$ go build -ldflags "-X main.GitCommit=abc" playground.go && ./playground
Hello world, version: abc

$ go tool nm playground
5242f0 D main.GitCommit
4c5678 R main.GitCommit.str

EDIT: it seems that the problem happens when case 1 is executed from a symlinked directory; when case 1 is executed from the original directory, the variable is passed. I'm not sure if this is expected, or it's a bug.