view remove: directly check whether specs own files before removing from view (#16955)

Bugfix for hardlinks and copies

var/spack/repos/builtin.mock/packages/needs-relocation/package.py

@@ -0,0 +1,28 @@
+# Copyright 2013-2020 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 *
+
+
+def check(condition, msg):
+    """Raise an install error if condition is False."""
+    if not condition:
+        raise InstallError(msg)
+
+
+class NeedsRelocation(Package):
+    """A dumy package that encodes its prefix."""
+    homepage  = 'https://www.cmake.org'
+    url       = 'https://cmake.org/files/v3.4/cmake-3.4.3.tar.gz'
+
+    version('0.0.0', '12345678qwertyuiasdfghjkzxcvbnm0')
+
+    def install(self, spec, prefix):
+        mkdirp(prefix.bin)
+
+        exe = join_path(prefix.bin, 'exe')
+        with open(exe, 'w') as f:
+            f.write(prefix)
+        set_executable(exe)