build: support pkg-config and link args

xtool/env/env.go

@@ -0,0 +1,32 @@
+package env
+
+import (
+	"os"
+	"os/exec"
+	"regexp"
+	"runtime"
+	"strings"
+)
+
+func ExpandEnv(s string) string {
+	return expandEnvWithCmd(s)
+}
+
+func expandEnvWithCmd(s string) string {
+	re := regexp.MustCompile(`\$\(([^)]+)\)`)
+	expanded := re.ReplaceAllStringFunc(s, func(m string) string {
+		cmd := re.FindStringSubmatch(m)[1]
+		var out []byte
+		var err error
+		if runtime.GOOS == "windows" {
+			out, err = exec.Command("cmd", "/C", cmd).Output()
+		} else {
+			out, err = exec.Command("sh", "-c", cmd).Output()
+		}
+		if err != nil {
+			return ""
+		}
+		return strings.TrimSpace(string(out))
+	})
+	return os.Expand(expanded, os.Getenv)
+}