all: Use Executable from os instead of osext (fixes #4900) (#4950)

vendor/manifest

@@ -198,14 +198,6 @@
 			"branch": "master",
 			"notests": true
 		},
-		{
-			"importpath": "github.com/kardianos/osext",
-			"repository": "https://github.com/kardianos/osext",
-			"vcs": "git",
-			"revision": "ae77be60afb1dcacde03767a8c37337fad28ac14",
-			"branch": "master",
-			"notests": true
-		},
 		{
 			"importpath": "github.com/kballard/go-shellquote",
 			"repository": "https://github.com/kballard/go-shellquote",