[WIP] relocate.py: parallelize test replacement logic (#19690)

* sbang pushed back to callers;
star moved to util.lang

* updated unit test

* sbang test moved; local tests pass

Co-authored-by: Nathan Hanford <hanford1@llnl.gov>

var/spack/repos/builtin.mock/packages/old-sbang/package.py

@@ -0,0 +1,35 @@
+# Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+
+from spack import *
+
+
+class OldSbang(Package):
+    """Toy package for testing the old sbang replacement problem"""
+
+    homepage = "https://www.example.com"
+    url      = "https://www.example.com/old-sbang.tar.gz"
+
+    version('1.0.0', '0123456789abcdef0123456789abcdef')
+
+    def install(self, spec, prefix):
+        mkdirp(prefix.bin)
+
+        sbang_style_1 = '''#!/bin/bash {0}/bin/sbang
+#!/usr/bin/env python
+
+{1}
+        '''.format(spack.paths.prefix, prefix.bin)
+        sbang_style_2 = '''#!/bin/sh {0}/bin/sbang
+#!/usr/bin/env python
+
+{1}
+        '''.format(spack.store.unpadded_root, prefix.bin)
+        with open('%s/sbang-style-1.sh' % self.prefix.bin, 'w') as f:
+            f.write(sbang_style_1)
+
+        with open('%s/sbang-style-2.sh' % self.prefix.bin, 'w') as f:
+            f.write(sbang_style_2)