switch darwin defaults using runtime.GOOS

To remove the need to duplicate the rest of the file.
diff --git a/fs/manifest_darwin.go b/fs/manifest_darwin.go
deleted file mode 100644
index ad502fa..0000000
--- a/fs/manifest_darwin.go
+++ /dev/null
@@ -1,30 +0,0 @@
-// +build darwin
-
-package fs
-
-import (
-	"os"
-	"syscall"
-)
-
-const (
-	defaultRootDirMode = os.ModeDir | 0700
-	defaultSymlinkMode = os.ModeSymlink | 0755
-)
-
-func newResourceFromInfo(info os.FileInfo) resource {
-	statT := info.Sys().(*syscall.Stat_t)
-	return resource{
-		mode: info.Mode(),
-		uid:  statT.Uid,
-		gid:  statT.Gid,
-	}
-}
-
-func (p *filePath) SetMode(mode os.FileMode) {
-	p.file.mode = mode
-}
-
-func (p *directoryPath) SetMode(mode os.FileMode) {
-	p.directory.mode = mode | os.ModeDir
-}
diff --git a/fs/manifest_unix.go b/fs/manifest_unix.go
index e1dd993..d2956f3 100644
--- a/fs/manifest_unix.go
+++ b/fs/manifest_unix.go
@@ -1,16 +1,24 @@
-// +build !windows,!darwin
+//go:build !windows
+// +build !windows
 
 package fs
 
 import (
 	"os"
+	"runtime"
 	"syscall"
 )
 
-const (
-	defaultRootDirMode = os.ModeDir | 0700
-	defaultSymlinkMode = os.ModeSymlink | 0777
-)
+const defaultRootDirMode = os.ModeDir | 0700
+
+var defaultSymlinkMode = os.ModeSymlink | 0777
+
+func init() {
+	switch runtime.GOOS {
+	case "darwin":
+		defaultSymlinkMode = os.ModeSymlink | 0755
+	}
+}
 
 func newResourceFromInfo(info os.FileInfo) resource {
 	statT := info.Sys().(*syscall.Stat_t)