external find for cpio (#19379)

* external find for cpio

* address reviewer comments

var/spack/repos/builtin/packages/cpio/package.py

@@ -4,6 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 from spack import *
+import re
 
 
 class Cpio(AutotoolsPackage, GNUMirrorPackage):
@@ -13,12 +14,20 @@ class Cpio(AutotoolsPackage, GNUMirrorPackage):
     homepage = "https://www.gnu.org/software/cpio/"
     gnu_mirror_path = "cpio/cpio-2.13.tar.gz"
 
+    executables = ['^cpio$']
+
     version('2.13', sha256='e87470d9c984317f658567c03bfefb6b0c829ff17dbf6b0de48d71a4c8f3db88')
 
     patch('https://src.fedoraproject.org/rpms/cpio/raw/dfe64c466d3ea2c8dfbd99700d9006f610064167/f/cpio-2.13-mutiple-definition.patch', sha256='d22633c368b8aedf4c08b23b6fbaa81a52404c8943ab04926404083ac10f1a4b', when='%gcc@10:')
 
     build_directory = 'spack-build'
 
+    @classmethod
+    def determine_version(cls, exe):
+        output = Executable(exe)('--version', output=str, error=str)
+        match = re.search(r'\(GNU cpio\)\s+(\S+)', output)
+        return match.group(1) if match else None
+
     def flag_handler(self, name, flags):
         spec = self.spec